1 - 2 Stunden
I got the YLOD right after I installed the latest software version on my PS3. I was about 5 minutes into a game when it turned off for no reason. I was angry since I had already paid SONY $180 to fix the blu ray drive before.
The repair did not take one hour. It took about 3. I spent a good bit of that time just cleaning the dust on all the parts. It was filthy. But the guide was easy to follow. To put it back together I would look for another video on youtube that takes you step by step. But in the end I got what I wanted and the PS3 worked.
BE VERY CAREFUL. I took 3 hours because I have never done anything like this before. I took time to separate all the screws, to clean the dust, and place every part carefully in a safe place. Make sure you do not mix up the screws and lock the cables in place.