20 - 30 minutos
My iPhone 3gs had been turning off randomly, even when the battery showed 80 or 90 % charge. It wouldn't consistently turn on again until connected to a power source. It was suggested that this could be a battery issue in several forums on the web.
I took the disassembly slowly. I had separate containers for each different screw type which really simplified r-assembly. I had to enlarge some of the pictures in the how to guide to see exactly what to do. The hardest part of the disassembly was getting the 'do not remove' sticker off. By far the hardest part of the reassembly was re-inserting cable #3.I'm still not sure whether I got it in all the way, but the iPhone works so I'm leaving well enough alone for now. I only completed the repair an hour ago so I don't know yet whether it fixed the problem, but I'm completely satisfied with the good instructions and the battery replacement itself.
I don't really have any advice, but I would like more advice on how to re-insert cable number 3 incuded in the instructions. The spudger and the suction cup were invaluable aids in completing the repair.