1 - 2 horas
I got the YLOD last week and we were already halfway thought the Skyrim and had no backup!
My husband thought there was no chance but we worked together and got the non backwards compatible 40 GB back up and were able to watch a blue ray movie and finish Portal 2.
The video is for a 60 GB backward compatible, so we had to go to youtube for the 40 gig tear-down. Also, the ifixit person did not say how far the heat gun should be from the board, so we just guessed about 8 inches on that.