Upgrading an intergrated graphics card

Where my fiance works he can get what he said is a Dell Inspiron 531 (I may have miss heard him or he may not of read it correctly because he was in a hurry) for really cheap.

He said that it has 3GB of RAM and 500GB of HDD.

HOWEVER, he said it has a Geforce 6150 se integrated graphics card and I know that integrated graphics cards aren't that great. So what I'm wondering is if we'll be able to upgrade it to something better (preferably not integrated) and what kind of options we'll have.

Edit: He says it has a PCI Express E_x16 slot.
2.8ghz AMD Athlon 64 x2 dual core processor 5600+

Thanks.

(We both game (mainly MMOs) and I do digital art.)