40 minutes - 2 hours
My ear piece speaker was damaged (from a previous tear down), and was near impossible to hear clearly out of - made the iPhone difficult to use.
Repair went well. Had some issues with the iPhone starting back up after install, but eventually it found its "brains" and started up normally. It kept indicating the battery was dead and needed to be charged - which was not true. Regardless, after a few minutes it was all back to normal.
Watch those screws. They be tiny, tiny, tiny.