M1530 graphic card upgrade

Hi everybody,

I have question for you all, so I would be glad to get as many answers as possible.

I have M1530 laptop, I have an issue with my 8600M GT (256MB). My laptop overheats in about 10 - 15 min of gaming or graphic operations ,  I solved with a cooler which works pretty good - shouldn't happen but whatever. Anyway my question is if you can this laptop (M1530) uprage with better graphic card . I am asking cause 256 is really not enough for example on Call of Duty 4 125 FPS I achieve only on lowest settings... when I shoot prolly around 80 which still is not too bad but I would rather have something where I dont have to play on 800/600 resolution. Would it be better to try to upgrade it with newer graphics card or just sell this laptop and try to buy a new one? I know changing it could b kind of pain but I think I could handle that. any suggestions? Also I don't have much money to throw around. I love this laptop very much but the graphics is just one thing what it missing to be perfect.

btw other spec: running vista (lowest settings), 4 GB ram, Intel Core Duo T9300 2.50 GHz with 6 MB Cache.

Any suggestion or help will be really appreciatte it! btw sorry for my english, I am foreigner ^^