At the top of the Technical Support Thread there is a sticky about how to set up for vista. I believe that all the "hows" are in there.
There are a lot of different video cards out there. As a rule of thumb I'd spend at least $100 on one. Less than that and you'll get a card that will work, but my give you trouble when you push it in the game. First find out whether our mother board takes AGP, or PCI express. I'm guessing PCI express because you have vista and the PCI express is the newer technology. Once your sure which "type" of card you need, go to Toms Hareware. They are doing write ups on video cards all the time as well as put up nice charts to compare card to card.