You may not be able to get more than a few hundred dollars for it. I was looking at computers just today. You can get a good notebook with about 120 gb harddrive (I forgot how much RAM but it was a pretty high amount) and build in wireless internet for about $1300.
As for what to get, I love Dells but HP and Toshiba are great too. I've had a gateway and didn't like it at all but they have improoved so I can't judge them.