Haxnetwork member NOkk3r1 has came up with a very simple solution to fix your YLOD PS3, with minimum disassembly and risks. His simple method adds pressure to the PS3 GPU and CPU via washers. You can read his post/tutorial here. He claims that he used this method on various PS3′s with good results on all of them.
Alternatively you can also view the heatgun method here (slightly more technical).