Repaired this iPhone 4 (CDMA/Verizon) twice. Teen girl squeeled twice.
1 - 3 hours
My daughter's friend's phone. Once she dropped it and this time another friend using it dropped it. I had to replace the front display both times. We have a STURDY case on order now. I even had to replace the Home ribbon cable this time.
Fantastic thanks to the iFixit guide. I took my time and it was about 90 minutes (a little faster the second time). Read all the warnings and cautions; you have to be very patient on a few steps for this particular phone. Get the plastic tools and ensure you lift straight up on the RF connections.
My trick: For the small parts I used an old plastic ice cube tray and labeled the compartments with the step numbers on tape. I used the kitchen table and worked on a sheet of computer paper to minimize ESD. Wish I had known: Removing the logic board would freak me out so much but it all went smoothly. Most important: When installing the front ensure the ribbons are (gently) pulled all the way through the frame.