1 - 2 hours
After many drops over the couple of years I've had this iPhone4s has resulted in a grey stripe down the side that just kept growing. I've repaired many iPhones in the past so I knew this was the time for a new display assembly.
The iFixit guide was very good though I found one place where I suggested an additional note on a camera lens that can easily come lose and get in the way.
I think a small set of bins or containers to hold screws as you take them off would be good to seek with every display assembly and tool kit. I think it should be recommended strongly along with the tools.
iPhone 4S Screen
iPhone 4S Replacement Battery
iPod touch (4th Gen) Headphone Jack