20 - 30 minutos
My girlfriend just had to have a white iPhone 3gs. We're still waiting on iPhone to go to 4G LTE. No we don't think that Siri is a good enough reason to upgrade. I got her a white 3gs and after using it for 20 minutes it shut off by itself. Craigslist burn! Looked online for a solution and found hundreds of people had the same problem and the majority of them recommended ifixit.com.
The repair went smoothly. Had to pay careful attention to the installation guide. It's real easy to miss a connection so take your time. Had to hunt down a suction cup to take the screen off but that was the worst of it.
I used one of those big lamps with the magnifying glass on it. It just made things easier. It isn't necessary.