30 minuten - 1 uur
Lightning connector was failing. Got the parts to update it. It was helpful to read the online ifixit guide before I ordered parts to see that I would be deep into the phone, so I figured that I would swap the 2yr old battery at the same time.
mixed results. Probably spent 3 hours on it. When opening the case, the lid poped open harder than I expected and it ripped the home button cable off. I ended up having to order a new part for that, (not ifixit) and the home button works, however the finger print sensor doesn't. The lightning connector part and battery went in as described in the online guides and worked. There are several standoff screws that were hard to find a proper screw driver, the guide could possibly describe the flat-head blade width and thickness, that would help.
Perhaps one of those clamps with two suction cups would have worked better at opening. However, by the time you do this much work on a phone, you have to ask if it would be easier to just buy a new one.
I was glad I was careful to mark out all the screws on a sheet of paper so that I could get them all back in the right place. There are many of them and it is very hard to tell which is which after they come out of the phone. I used a sheet of paper, and wrote on it for each step, and which screw and tried to keep the screws on the page next to the notes. This worked pretty good at keeping everything organized enough that I could get it all back together.