20 - 30 Minuten
I gave my daughter my old iPhone 3GS to use as an iPod. It worked fine for about a month but then started not working unless plugged in. And it got fatter. And fatter. Until the faceplate popped out of the shell and the back started showing a bunch of tiny cracks.
The "geniuses" in the Apple store told me there was nothing to be done, it then I saw your website and ordered the replacement battery. It arrived a few days later and I followed the on- line directions. The whole exchange went swimmingly and now the 3GS works as well as ever. Everyone's happy!
Keep careful track of all the little screws and be careful of the connectors when reinstalling the logic board--I almost crushed one.