I do not think it is easy to upgrade laptop graphics card. Most laptop's graphics "cards" are on board, so most possible to replace. Some laptop use mini agp card, they can be replaced but I think it is almost impossible to find anyone sell mini agp card to retail customers. You may be able to find some company do it for you, but it would be too expensive to think about it.
If you really want to use laptop to play games, see the one you got and buy another one from novatech, ajp, dell etc.