1 - 4 horas
I simply wanted to boost my Imac by adding a ssd drive
It took me almost 3 hours (it was the 1st time), I was a bit stressed to break something but just relax...print the instructions and try to have the video tutorial next to you and nothing wrong can happen.
Don't go too fast when you re-assemble the imac ! I did it and when it was almost completely done I realized that I forgot to put back a lot of screws ! ;-)