My iphone 3G battery was totally dead/unresponsive. I wanted to fix it so my 5 yr old son could use it as an iTouch, but didn't want to pay what Apple charges. After I saw a story in the nytimes about ifixit.com I decided to give changing the battery myself a try!
It went well! I feel so empowered and it was easier than I thought it would be. It took longer than I thought- around an hour partly because when I was reassembling I accidentally trapped tab 5 under the board and didn't realize it until I'd already put almost all the screws in. My favorite part of the entire process was removing the screw under the sticker that said 'do not remove!'
Overall- awesome instructions! My only problem w/ the instructions was that I found it difficult to understand how to remove tab 3 connector. I think a close up would be helpful. I thought I broke something when I finished that step! It was also very difficult to put #3 back in though I don't have any advice about how to make that easier other than to take your time. The most helpful tip I read was to put all the screws on a fridge magnet to keep everything in order.
iPhone 3G Replacement Battery
Phillips #00 Screwdriver
SIM Card Eject Tool