15 minutes - 1 hour
My phone kept shutting off by itself whenever my battery got to less than about 30%. It wasn't consistent, and it was incredibly frustrating having it shut off with no warning.
The biggest headache was prying the screen off, BY FAR. Read on for some tips that might make your replacement much easier.
So after struggling with the screen for over half an hour, I finally read a comment on the guide made by a previous user that suggested prying near the headphone jack. This made a HUGE difference. The display popped up nearly instantly!