10 - 30 minuten
My iPhone 4s battery was over two years old and just not holding the amount of charge that I needed.
I ordered the battery replacement which came with the tools necessary to do the job. The kit also came with the "liberation" screws. I also watched several how to videos on battery replacement. While watching the videos and using a table top magnifying glass, I was able to have the repair done quickly. I experienced no problems at all. I powered the iPhone up, it searched for a signal, found it, and I was off and running.
Take your time in doing this repair. Watch several videos, get a magnifying device, and find a quiet place to make the repair. Wear latex gloves if you have some to cut down on dirt and oils from your fingers. I would recommend also having tweezers on hand. Also, do your work on a flat surface that is covered with a cloth or maybe a pillow case. Use the least amount of force necessary when removing the back cover and when prying the battery. Hopefully your battery replacement will be as smooth as mine.