20 - 30 minutos
Well I have a old 3GS that I have been hanging on to since it came out. I constantly tether the thing so I suspect that is why the battery would not hold a charge. Eventually I could barely do anything with my phone unless it was actually plugged in. So I ordered a new battery and waited. During this wait time, I was coming home from the gym and as I was getting out of my car, my hands were a bit shaky and dropped my phone on the ground. For some reason I also decided to take my case of my phone...resulting a smash screen. Needless to say I then had to order a new screen as well.
Repair went smooth except I was a not paying attention to detail and ordered a battery for a 3G not 3GS. Kept the "old" new battery and ordered the proper one. Repair went smooth with no issues. I came to being soo good at it as I had to do it multiple times, due to me thinking something was not installed correctly when it was actually the wrong battery. I now do not need any guide to install a new battery on a iPhone 3G/3GS.
Make sure you order the proper battery!!!