My iPhone really dislikes being cooped up in the side pocket of my bag, so one day it decided to jump on out of there! It freefell a whole three feet to the wood floor, where the back coverglass sustained a moderate cracking injury. After the fall, I palpated some small shards of glass that were coming loose.
Easy peasy! I used my friend's pentalobe screwdriver to remove the old panel and discard the cracked panel in our sharps container at the hospital where I work. I then replaced the rear glass panel with the new one and screwed that sucker in!
Know how to remove the rear glass panel before taking the screws out. It took me a little while to get the old panel off. (it slides towards the top of the phone.)