1 - 2 horas
YLOD on my PS3 came while I was playing
I followed the repair manual, which it is fantastic, and bought the YLOD Fix kit, which have everything you need, and now my PS3 is working again :)
Watch carefully the video and the photos in order to do not make a problem with your PS3. Take your time while reflowing the board, I spent around 1:30 min applying hot air to the board.