20 - 30 Minuten
After I purchased my new iPhone, my trusty 3GS started it's journey down the family tech tree. My wife has been using my old original iPhone as an iPod replacement and complained that the battery on the 3GS didn't last nearly as long.
It went quite well, and was easy to perform.
When disconnecting ribbon cable 1, insert the spudger under the cable and pry up. The spudger used in the photos is black so it's hard to see what is occurring. The Do Not Remove sticker only has to be removed enough to get to the screw. I had a hard time trying to get the sticker off.