Europe - Need advice on passing through customs/immigration from USA to Ukraine

I live in Atlanta, GA. I am planning to take a vacation in Odessa, but I have never traveled overseas before. Several "unknowns" have me concerned, and I'm wondering if anyone can share their knowledge.

1. I will probably change flights and airlines a couple of times. My best ticket prices have routes like, Atlanta to Toronto, Toronto to Vienna, and Vienna to Odessa. If I do not speak German, will I be able to read the signs to find my way around the airport in Vienna?

2. How many times will I go through customs / immigration? Only when I arrive in Odessa? Or do I go through this in Toronto AND Vienna AND Odessa?

3. Reading other posts from people who stood in long lines and almost missed flights, what kind of layover time should I look for at these airports?

Not sure what happens in Toronto on connecting flights from the US. Will let someone else deal with that. In Vienna, you will be making a non-Schengen to non-Schengen connection, so no immigration needed. Try to make sure your bags are checked through all the way, so you don't need to collect them until you get to Odessa.
In Vienna enough of the signage is in English to allow you to navigate through the airport. It's much smaller than either Atlanta or Toronto. Ideally you want to try and ticket this with one airline or within a single alliance as that gives you more chance of help if things go wrong and your flights have more chances of being in the same terminal.
On the airlines you book with, you should see what the minimum connection times (MCT) are at each airport. If you want to play safe, you might want to add some margin. However, I doubt there are many flights per day between Vienna and Odessa, so you may not have much choice in the matter. In any case Vienna is pretty good at short connections.

Thanks 'catandmouse'. This is very helpful, and makes me feel a little better knowing what to expect since it is my first time traveling overseas. It's good to know I'll be able to navigate Vienna. If I can stay with one airline, that would be ideal, but sometimes the cost of the tickets is prohibitive. For example, if I look on Orbitz, there are many round trips in the $1500-$1600 range. If I stayed with Air France for both round trips, it would cost over $4100 for the same trip. I'll also check the "MCT's" as you described to make sure when I book my flight, I leave enough time between them to be realistic. That only leaves the question of whether I need to pass through immigration in Toronto when for my connection to Europe.

In Canada, you will need to present yourself and passport to a Canadian border agent, and then pass on into the secure area of their airport.

They will probably ask you a few questions on the nature of your trip and determine if you have the funds to be admitted to your final destination. A printout of your itinerary may be helpful here.

You will not need to clear customs until you reach Odessa.

Make sure you have at least an hour (safer 1 1/2 hours) to pass through Canada between connections and possibly an hour for Vienna. Vienna airport is not very big.