Easier than I expected--even a software person can do it!
15 minuten - 1 uur
Any time my battery got below 50%, it was a matter of minutes before it would power itself down and not turn on again until connected to its charger. The phone is out of warranty and I have no AppleCare. I discovered after ordering the new battery that Apple had announced a recall and my battery was among those they had identified as defective. I may still have been eligible for a free replacement, but decided I might as well try to do it myself.
I was a bit apprehensive after watching a couple of videos where the original battery seemed to have been attached with Super Glue, but that turned out not to be an issue with mine.
I skipped steps 9-12 (detaching the three connectors attaching the front panel assembly from the rear case). I was probably able to get away with this because there was hardly any adhesive on my battery and I didn't have to use the spudger to pry the top of the battery--just the side. I didn't have to use the pull tab at all.
The hardest part for me was getting the front panel assembly away from the bottom case, but I was being extremely careful, having read prior comments about the danger of yanking it away and damaging the ribbon connectors.
Everything works, and I no longer experience any anxiety when my charger and my Mophie case are out of reach.
Heed the comments in the guide about being careful with the itty bitty screws. I used the magnetic project mat and did the disassembly and reassembly on a piece of foam so nothing would bounce or roll away, but I still managed to (temporarily) lose the 1.8 mm screw while reattaching the battery connector bracket. After crawling on the floor for five minutes, I found it in the case between the battery and the pull tab.