I have a PS3 fat 60gb that had YLOD, and I made the reflow and IT WORKED, is still working after six months. I can assure you that it works and is not like you will break it for sure, the thing is that you need to know how to do it carefully. My first advice would be to completely disassemble the PS3, and work only with the Main Board. Second advice: first heat the board evenly to a certain temperature, And then heat the GPU and CPU units. That is because if the board is cold, and you heat the proccesors only, the part of the board where the processors are will expand but the rest of the board will not. And if that happens some circuits might break, making the board useless. And one more thing, for me it did not work the first time that I tried, I think becaused I was a little afraid of burning something up, so I did not use full heat the first attempt. However I inmediatly tried again when I saw it didn´t work but the second time I placed it full heat. And then it worked!
Funny fact: I do not have a heat gun so I actually did it with my sister´s hairdryer XD