5 - 30 minutes
Both my daughter and I had iPhones with batteries that would not last the day. 30% by 2:00pm. Six screws in less than 10 minutes and I had both batteries replaced.
Great. Easy to complete.
Use a dishcloth as your work surface. It will help you keep from loosing those tiny screws if you drop one.
iPhone 4 Replacement Battery
iPhone 4 and 4S Power and Lock Button
iPhone 4 (CDMA/Verizon) Power and Sensor Cable