20 - 30 minutos
I had my iPhone 3GS for over 2 yrs now and recently the battery has started dying. Rather than pay the Apple to do this, I figure I could save some money and do it myself. My brother purchased the same replacement battery and claimed it was fairly easy to do and being a guy who likes to take things apart and put them together again I decided I'd give it a shot.
The repair went smoothly. Only step I had trouble on was peeling of the sticker that says "do not remove." In the end it proved impossible to remove this sticker without damaging it.
Advice to anyone doing this is to take it slow if your are replacing the battery for the first time and read the guide. Some of the connectors do appear fragile but once you've done it once, the operation should feel like second nature.