10 - 30 minutes
Since upgrading to iOS 7, my iPhone's battery life has gotten worse and worse. Once it reached about 7%, it would suddenly die. Online searches revealed that it's a software problem -- but this battery is about 2 1/2 years old, so I tried this kit. It definitely worked! Battery life is just like new and the phone is working perfectly. It wasn't a software problem after all.
The kit came with everything I needed. A magnifier, tweezers, and alcohol-soaked QTips would have helped. The high res image helped me understand how to replace the small pressure contact.
Connect the battery first, and then slide the pressure contact in place. You slide it under the battery connector's upper screw hole.
The old battery is held in place with double-sided tape and it takes some effort to remove it. Be patient and take your time.