Captain Over,
Replacing the Video Card on a Notebook is very tricky. First as goates points out, it needs to be a card that is not hardwired to the motherboard, and second, you have to find another notebook video card, that will fit it.
Finding a video card for a notebook will be very difficult and I am guessing, very expensive. If you are able to, try to find the Radeon Mobility 9600, it does a great job with graphics.
Please let us know what you find.
Take Care,
Richard