My wife's phone. She cracked her LCD screen
The "Ifixit" video manual was to the point and quite accurate except a couple of things. On this particular phone the original adhesive refused to let go after heating the chassis several times. The iSclack was not strong enough to lift the rear cover loose and i ended up using a razors edge. However I couldn't prevent the rear cover to crack on one corner. The second obstacle was also related to the original glue. The battery also wouldn't let go and I had to use the same razorblade again. I found the whole process relative easy and the only thing giving me real headache was the original adhesive/glue! Due to being a newbie and doing this for the first time I really didn't know what to expect and I forgot to order the replacement adhesive for the new screen. However I got that from a local repair shop who helped me out despite they do not normally deal with phones.
The instruction video says/shows litte about how long and exactly how the heat gun should be used. When I got the phone opened I saw that the adhesive is strictly around the surface edges, so that's where the focus should be pointed. It probably should be heated to the point where you almost can not touch it anymore with your fingertips. And hurry with the iSclack! When you order a new screen, do not forget new front/rear adhesive!