1 - 2 hours
My Wife dropped her iPhone for the 100th time, and this was the time it shattered the screen.
The first time I tried, everything went smooth; till I was plugging some of the cables in; One cable seemed to come up short; I soon discovered that something I had done had sheered the thin cable and it was ruined. I ordered a second screen and this time everything went perfect!
Take your time when putting it back together; make sure you have a good way to keep track of your screws.
iPhone 4S LCD Screen and Digitizer
Flathead 3/32" or 2.5 mm Screwdriver
P2 Pentalobe Screwdriver iPhone