2 - 5 minuten
Broken rear glass and vibrator motor on my dad's iPhone 4.
Replaced both in under 10 minutes. His frame was bent a little from a drop so it was a little hard to get the new rear glass on (plus I might have forgotten to take off the plastic cover on the inside the first time...) but I got it to fit.
Don't forget to take off the plastic covers on both sides.