1) you would need to buy an upgrade. But there should be no reason. Home edition should work perfectly well for all your needs.

2) Almost every laptop will have at least 1 slot open to install more ram. You would need to look at the manufacturers web site to find out how much and how to install it. Actually ram is a big saving if you buy 3rd party ram instead of oem. I just bought 512 MB additional ram for my private spare laptop for around 40$.

3) I would probably not buy refurb looking at how inexpensive you can get brand new models. I would buy slightly older models, e.g. the IBM T42 (ok Leonvo ) is a very nice laptop and there is hardly any difference to the T43. By not buying the greatest newest model you can save a bundle and won't really loose out this much.

4) For me technical specs really don't matter this much. Consider that the processor is the same for all (either Intel or AMD), the hard disk is from a similar manufacturer with similar specs, USB is USB, whether your CD writer does 12x or 16x speed hardly matters. Almost every laptop should have what you need. I would look at reliability, general look and feel, repair history, how much a 3 year warranty is (a laptop is one of the view things I would buy extended warranty for).

Also in my experience if you buy on your own money you are better off buying the second best cheaper model and rather replace it a little earlier. Instead of spending 2000$ on the newest greatest you can spend 1000$ now, resell it later on fleabay and buy a new one. Even your 2000$ model is outdated when you unpack it. I would also look at the keyboard, screen etc. Also do you plan to watch DVD's (movies) on it ? If you do that a lot a wide screen model might be nice.

I have very good personal experience with IBM laptop's and really like their look and feel (nice keyboard, etc.) but they are pricey.