My experience repairing these MBPs (C2D with 8600GT GPU) is that you get once chance to repair the GPU, effectively, via a DIY method of heatgun + flux + level surface + a slathering of good luck, experience and timing. I repaired a 2.4Ghz model with no issues and works well, but another (the first one I repaired) I needed to go in again and again before I decided to call it a day.

Lots of local notebook shops have a BGA reball station which I'd go for over doing the DIY method. I didn't have much to lose with mine so decided to cheapen out and try repairing it myself.

JB