5 - 20 minutes
Cracked my screen dropping it out of my shirt's front pocket. I lived with the cracked screen for a while, but then the vibrator broke, so I thought I might as well kill 2 birds with 1 stone!
It went quite well. The display assembly actually was kind of broken when I received it. The screws holding in the front facing camera were not tight and therefore the metal bracket holding it on was all bent up. I had to take it off, re-bend it, and screw it back on. I managed to do this correctly, replace the vibrator, and the screen in about an hour with otherwise little trouble.
Make sure you have patience and plenty of time to do this. Sometimes it can be frustrating to push the screen back in but WHATEVER you do, do NOT force it in. If a corner does not snap in, pull the screen back off and try it again, and again, and again; as many times as necessary to get it back in.