I used the gilksy tutorial while trying to revive my friends ps3 and it worked like a charm:
ps3 ylod fix part3 gilksy - YouTube
Also it's very important that there's good contact between the cpu/gpu and the heatsink. Check this out, worked for me when I had green light of death (no audio/video but ps3 stays on)
http://www.ps3hax.net/showthread.php...145#post102145
And finally, how to apply therma paste correctly with good contact:
PS3 Arctic Silver Proper Application on Heat Sink - YLOD Prevention - YouTube