20 - 30 minuten
After roughly 4+ years of continuous use my iPhone 3GS started abruptly turning itself off (at the most inconvenient times). After searching around on the Net it appeared the general take was that this normally happens when the battery is on its last legs. I figured for $20 it was worth trying to perform the surgery if it meant keeping my phone for another 6-12 months. So I went for it.
The repair went OK however as with all repairs, taking the thing apart is not the problem. The problem is putting the device back together again. Like some other folks here I had to take the phone apart all the way down to the motherboard a number of times until I got the assembly right. There are a number of issues to look out for that are not covered in the instructions. If I had known about them it would have made the reassembly process quite a bit easier.
First, aside from the written instructions on this site, I recommend finding a video tutorial on YouTube to follow as well.
This one helped...
Some points to consider when you're putting the phone back together:
1) Success in reassembly is 90% getting that motherboard connected right initially. Really look at the connection up at the top to your camera. If you're not sure if it clicked in right, unscrew the camera completely and attach it securely to the motherboard first.
2) Make sure the motherboard is absolutely flat and flush with all the screw holes. The best way to ensure this is to see if the SIM card will install smoothly from the top.
3) Generally speaking the screws are all very small. What helps is that there is some magnetism going on so you can usually pick them up with your screwdriver and they stick while you are screwing them back in. Trust me though, you want to find a secure receptacle to store these while you are performing the battery replacement. These suckers are easy to lose and if you lose any of them you're "screwed"!