20 - 30 minuten
Four months ago I replaced the iPhone 3GS battery with a $6 cheapy. It was buggy from the start. Phone crashed when charge got down to around 70%. After a couple months, it crashed at 90%. Crashed at 99% in cold temps. Any use of video would crash it. So i got this battery from ifixit to replace a bad replacement.
Repair was easy and fun because I had done it once before. ifixit's guide is awesome, though, and I wish I would have found it the first time around.
Use a suction cup on the iPhone glass to remove it. I use the suction cup for my car's GPS device, and it works like a charm. Do not pick away at the edges of your phone trying to pry the glass off - you will only wreck the edges. Use a suction cup. Also, remove the glass from the home button, hinging it at the top by the sleep button. Otherwise, you risk breaking the wires at the top of the phone. Finally, in addition to whatever tiny tool kit you use (I used a plastic set that came with my first cheap replacement battery), include a pair of tweezers just in case your fingers get shaky.