1 - 3 horas
My girlfriend has an HTC Inspire that she has a lot of problems with so I wanted to surprise her with a 3G S for Christmas. The back cover was a little scuffed and had a crack near the connection port so I ordered a replacement white back cover for it.
The repair went great! It was actually a lot easier than I thought it would be. I definitely recommend the tool kit iFixit sells. It made everything so much easier.
Overall the guide was great. One thing that should be added though is something about the screens for the speaker holes. If you don't get them off the old back cover than you will just have two holes where the speakers are and debris will get into your phone a lot easier.