20 - 30 minutos
Screen was cracked and battery had diminished life.
Repair was smooth. Watched the videos for iPhone disassembly a couple of times. The most difficult part of the whole process was separating the shattered glass from the support frame. I purchased the front panel glass-only assembly since the display and button were still working fine despite the shattered glass.
The final result is a phone that looks and acts brand new.
It definitely helps to have a good pair of needlenose pliers available to assist in getting the screws positioned for reassembly.
I did not use a heat gun/hair dryer to soften the adhesive in order to separate the glass. I used a razor scraper with a razor blade (see image). It was tedious work but I didn't risk melting the button or anything else. I would advise putting a brand new blade in the scraper and placing the front panel on it's side. Take your time and be careful not to cut yourself. It helps to make sure you're always moving the blade away from you so in case you slip you're not going to gouge yourself (Boy Scout 101).
Even though this method is time consuming I think the finished product is worth it and this is a lower risk approach than the "melt it off" heat gun method.