2 - 5 minutes
Broken glass back on old iPhone 4 was making me sad (I want someone to give it a good home and knew it needed some TLC)
Took all of about 30 seconds - perfect fit, screws provided and now the phone looks like new!
Read up or find a YouTube video. There are thousands, and this repair is sooo easy. A word - the screws are TINY. Put them in a magnetic bowl or on a piece of tape so you don't lose them. Happy repairing!