Gateway 7325 Overheating problem

I have a Gateway 7325GZ laptop that is chronically overheating and shutting down. I purchased a cooling pad but that doesn't even really help the problem either. I'm pretty sure that both fans are working, but I've been told the heatsink sometimes isn't seated properly and that could be the problem. I have looked around online and on Gateways support and haven't been able to find a 7 series disassembly guide or anything about replacing the fans/heatsink. I downloaded SpeedFan and right now my HD is at 51C and Temp1 is at 77C. Usually if the cd drive is working (ripping cds to iTunes, watching dvds) or I am watching videos online is when its having the problem. Does anyone know of a fix or a way to upgrade the fan/heatsink? Or does anyone have a guide to access the fans/heatsink. Any help is much appreciated.