Why not rent the car right at CDG, see Giverny at your leisure and drive on to Rouen?

And don't forget about the Annecy/Chamonix area ;)

We went to the window to change a ticket.

If you're looking to save some money and waste some time going between CDG and the city centre, you could always take the 350 bus to Gare du Nord/Gare d'Est. It only takes an hour or so.

If you do that (an excellent idea, by the way, speaking as someone who loves both Rouen and Giverny), make sure that you pick up your rental car at the TRAIN STATION at CDG. For some reason, the pickup fees/taxes/something are lower if you get it at the train station office than at the airport office.

(We discovered that by accident several years ago.)

There are some trains that require a reservation/ticketing in advance. If you hop on without a ticket, you will pay a penalty.

First class is a lot more comfortable than 2nd. Whether they're worth the price difference is a matter of preference (and related to the length of the journey).

Generally, tickets purchased in the US through raileurope are a bit more expensive than those bought in France at the station. But it varies. Do not buy through the SNCF website unless: 1. it's one of the tickets that you can print out online; 2. you have a French (or other European) credit card with a chip; or 3. you will have time to queue up at a ticket window to pick up your ticket using your US credit card.

The point was that I have to get to Gare St. Lazare. I could take the RER (or bus) to Gare du Nord, but I would still have to take the metro (or walk) with luggage to St.L. for the train to Rouen. Likewise, if I want to take the train to Beaune first, I would have to get to Gare Lyon; the AF bus #4 goes to Gare Lyon as does the RER with one transfer from what I can tell, or once again I could take a taxi.
I definitely could still drive all over, as I was considering in my original post, but many here advised against it. To get from Giverny to Beaune, I would have to drive around Paris but I assume the perimeter road is not so bad, unlike downtown.

Rent a GPS with your rental car. You will have no trouble. Driving right from CDG really would eliminate a lot of unnecessary carting of bags, navigating metros, RERs, not to mention the saved time and money.

If you decide to go to Beaune first, the AF bus is the simplest other than a taxi. Check out the prices of each.

If you're going to Rouen first, I would definitely pick up the car at the airport. Driving around the Paris perimeter is no picnic, but it is doable.

Not sure about the money saved, since they do charge more to rent at the airport, even the airport train station from what I can tell.

To give you an idea, here is what I found, in USD.
Train, RT Paris Roue/Vernon is $83 pp, plus I'd estimate $50 for a taxi to Gare St. Lazare.
Train RT, Paris/Beaune is as low as $155. Incidentally, I priced the TGV southbound and a regular train northbound, which is less expensive but slower, naturally. Also, all prices are second class/flexible except first leg. I would guess about $30 for a taxi from St. Lazare to Lyon. I understand the #20 and 24 buses make that trip but are not convenient especially with luggage.
Alternatively, it appears you can take the RER from CDG to Lyon, switching B to A, if I were to go to Beaune first. On the second I would need to get from Lyon to St. Lazare.

In contrast, europcar quoted me $283 for four days for their least expensive car, no additional insurance, $330 including a GPS. autoeurope quoted $249 to rent at CDG, or $206 to rent at Gare du Nord and return to Gare Lyon. For some reason I could rent at one gare and return to another but the website wouldn't let me rent at the airport and return to a gare, and it would let me reserve a GPS but did not include it in the price. That does not include a second driver charge either. Obviously, gas would be a major additional expense and I see there are some toll roads involved.

So for two people trains plus taxis exceed $500. Car rental would be about half that before gas.

You've got some great advice here, so there's nothing new that I can really add beyond what's already been said.

However, I'd like to comment on a couple of your questions and a couple of the comments made in the thread.

First, I'd second the recommendation to consolidate your time in Paris at one end or the other. I wouldn't do Paris for a day at the beginning--the stress of getting into the city and navigating to your hotel is not going to do anything to recharge your travel batteries! Much easier just to arrive at your final destination and then crash.

While as someone already said it's impossible to not stand out, it's still a good idea to minimize your appearance as a tourist. It's not uncommon (from what I saw) for people 30+ go around with a handbag or satchel of some sort. Under 30 wouldn't be out of place with a backpack. I alternated between backpack and just stuffing stuff in my coat pockets (it was winter, so I had that option), and I definitely felt more comfortable when I didn't have a backpack.

And be especially cognizant of your surroundings in crowded places. Right as we were leaving Paris for ORY, I was actually the victim of a pickpocketing incident on the Metro. Fortunately, my traveling companion had the presence of mind to see what was going on and actually smacked the guy right before he tried to open the door of the car to disembark. It stunned him long enough that I was able to snatch the pickpocketed item back before the door opened. Of course, we were obviously tourists, since we had our luggage with us.

Agree. Overhead racks are much less roomy than Amtrak's. There are luggage racks at one end of each car, so carrying luggage on the train isn't impossible--just difficult. (No checked luggage on the TGV as far as I've been able to tell.)

If you're reasonably comfortable navigating public transportation and really are on a budget, I think you could manage the RER/Metro. On my recent trip, we took the RER from ORY to Gare de Lyon and we survived just fine. (This wasn't my first time in Paris, although the only other time I'd been there was 10 years earlier, by car with my grandfather.) Of course, it wasn't easy, considering that it was the morning rush hour and a broken RER train at Antony that dumped all of its passengers off made the process pure chaos (so navigating around the jam-packed station with our bags wasn't easy, and we had to wait for the third train before we could get on), but we survived, and once we got off the RER B at Chatelet Les Halles and transferred to the RER A to GdL, things were much smoother. I'd still do that over a taxi to save 30-40 EUR... :)

TER is Transport Express Régional. They are mainline intercity trains across France but travel slower than TGVs and stop at more stops. They're perfectly comfortable (the TER coach I rode in from Beaune to Dijon was actually more comfortable than the TGV seat from Paris to Dijon), but your trip will take longer, and 100mph isn't as much fun as 186mph... :D

In addition to this, TGV fares aren't a set fare between a given city pair (like LIRR or NJT tickets). They're more like airline fares and fluctuate up and down based on demand and how early you book. It is generally (though not always) advantageous to book earlier rather than later, as you can get much better prices with advance purchase tickets (with the exception of some last-minute deals). So yes, you can wait until you are at the train station to buy the tickets, but you'll likely pay a higher fare than if you had booked them two months out, plus you chance your train being sold out. I speak from experience: I actually tried to buy tickets on a Saturday night on my iPhone but couldn't complete the transaction until Sunday afternoon when I was on a real computer, and the price had gone up about 20EUR in the meantime.

I booked through tgv-europe.com (basically an English-language version of the SNCF site that, IIRC, only books TGVs, not TERs, night/hotel trains and other slower trains) and had no trouble picking tickets up from the window at Gare de Lyon. There was no line, and the agent was very friendly and helpful. (Side note: even if you're a dumb American who speaks absolutely no French, I learned that a respectful, humble look accompanied by the words, "Bonjour [bonsoir] madame/monsieur, parlez-vous anglais?" with at least an attempt at proper pronunciation works wonders over the more typical American "Hi, do y'all speak English here?". Given that you can mungle around in at least a little French, you'll probably have little problem with getting people to respond in a helpful fashion.)

Ah, but you can! It's a simple single-transfer ride either on the RER B to Gare du Nord to the RER E, or the RER B to Chatelet Les Halles to the Metro line 14. The RER B is jam-packed at rush hour (as I mentioned above), but it is certainly doable, if not overly comfortable. (Transfers between RERs and RERs and Metro lines at connecting stations are generally pretty easy. I wouldn't worry about "still hav[ing] to take the metro (or walk) with luggage to St.L. for the train to Rouen."

And if you decide to go to Beaune first, you can take the RER B to Chatelet Les Halles to the RER A to Gare de Lyon. This is (based on my experience) a very simple transfer.

Two ways to find out how to navigate the RER/Metro:
http://www.ratp.info/informer/anglais/index.php#
and, for the more visually inclined, http://www.ratp.info/orienter/cv/carteparis.php

This sort of question always elicits debate, whether it's SNCF, Amtrak, or whatever. It's really up to you whether you really think extra room is worth extra cost. Me: I like bigger seats, but when it comes to the budget, I'll stuff myself in the smaller one unless the fare difference is so low as to make it a no-brainer.

I will say that the TGV coach seats are probably going to be smaller than you're thinking. (They're certainly smaller than I remember, but then again, the last time I rode in one, I was about 15!) They weren't uncomfortably small, but the legroom was not conducive to anything other than feet-planted-firmly-on-floor, and the width was adequate but not generous. I'd say it's even less room than coach class on an Amtrak Regional train--certainly not anything near the [small plug] better-than-airline-domestic-F coach seats on a long-distance Amtrak train!

Anyway, you certainly have a great trip planned. Even though I just got back, I'm envious and wish I could stow away in your luggage! :D

Have you checked the Avis website? We've found them to have (sometimes) very competitive rates, and you can get quotes for CDG pickup and G de Lyon return (although it may take a little digging).

Thanks. After I posted my earlier comments, I tried Avis. Their rates were very good, but I couldn't find a way to book at an airport and return anywhere other than an airport, at least booking online, but that may be just me.

Regardless, it is all moot. My wife thinks the train will be more romantic (probably right), and jackal led me to some sites that should make the cost more bearable.

BTW, I looked at the sncf site and the prices were quite good, but I didn't want to rely on my French. I think I could do it, but it just seemed too likely that I would miss some T&C that could haunt me.

But the train it is. I still have some train questions, but I posted them in the Europe by Rail forum. I also have some wine questions (yum) but I will start a new thread.

Thanks FTers.

I think the tgv-europe.com site and the voyages-sncf.com site are similar enough that you can read the T&C on tgv-europe.com and be pretty confident that they're the same on voyages-sncf.com, since all of the other fares seem to line up (the ticket classes are even called the same thing on both sites). The only difference between the two is that tgv-europe.com only books TGVs and voyages-sncf.com will book all types of trains.

I don't think you'll find French train travel very romantic, but hope that you'll enjoy it anyway.

If you change your mind about renting a car, post again and I'll try to help you find the page on the website that lists the train stations.

Hope you enjoy your trip- that it will be memorable in all the best ways.

That is the sound of me chewing on my words.

I just booked those train tickets on the sncf site. I had great difficulty with the tgv-europe site for some reason. I am satisfied with the price and the times should work fine if I can get from CDG to the gare on time. It looks like I can do the four day excursion for about 220eur, which would have to be less than a car if you include gas.

So Mrs. DennyO met a woman from Paris the other day and told her about our upcoming trip. Among other things, the subject of public transportation came up, and this nice lady told Mrs. to take the bus. Why, she asked, if you are on a rare visit to a beautiful city would you want to take the underground when you can get to your destination and see the city at the same time?
The metro is (sometimes) faster, I thought, but beyond that .... I am stumped.