20 - 30 Minuten
My wife's phone would not charge and the home button did not work.
After checking I determined that the battery was worn out. I ordered a replacement battery from iFixit and the necessary tools. The replacement was relatively easy. I had problems with connector 3. It broke off. I tried the phone any way. It amazingly worked. The home button worked also.
Keep the screws separate and in different containers. The instructions for removing the connectors need to emphasize lifting the edge of the connector upward. #3 is still a mystery. Need more info.
iPhone 3GS Replacement Battery
Phillips #00 Screwdriver