Its not too difficult to put in a new video card. If you have not done any work inside your computer before, it would be advisable to read about it . . . maybe cruise some websites on building your own computer. It is basically a matter of uninstalling your old video drivers, putting in the card, and installing the new drivers.
It would be important to know a little about your motherboard and your computer. Does your motherboard require an AGP card or the new PCI express card? It would probably help forum members to know your computer's specifications first before recommending a video card (type and speed of processor, memory, etc). Knowing about your budget would also help. There are some fairly good video cards (such as the 7600 GS) that can be had for about $100. The sky is the limit, however, with cards going up to 400-500 dollars for top of the line.
It would also be helpful for people to know what kind of gaming you like to do with your computer and the size of your monitor as these factors determine how powerful a card you will need.
Regards,
DeeJay:beard: