Definitely worth doing. Take your time and be circumspect about every step.
Yes, test fitting is very important. I laid the old battery in and out several times, looking at it from all sides, then laid the new battery in SLOWLY and deliberately.
Remove the haptic engine! It’s the easiest part of the repair and gives much easier access to the adhesive.
One of my strips came out cleanly and the other broke. I very carefully worked the edge of the battery up (with the spudger) until I could see the broken strip, then grabbed it and pulled again. It broke again—several frustrating times—until I finally got a good hold on it and it gloriously pulled free. Keep at it this way; it’s much easier than working a card under the battery, which could easily damage the display clips.
I’ve done this with an iPhone 5 and an iPhone 6S. I did not remove the display either time; I was afraid of damaging something unnecessarily. It’s definitely not necessary to remove it! I had an extra set of hands and eyes to help me be careful, but if you get the battery adhesive strips off cleanly, it’s easy to leave the display on.
Heat is essential, and take it very slowly. Also take seriously the instruction to open just enough to get the spudger in there—then do the real work with that. The suction is just to get started. I had my son insert the spudger as soon as there was any gap at all, then worked it according to the guide.
I did this on a card table with a vinyl surface so I could lay the phone down. Then I held the metal frame on both sides while pulling the suction cup—my son having the spudger at the ready. Definitely be patient! I had to restart several times when the suction cup popped off and I accidentally reengaged the clips pressing it back on.
This was the most uncertain part of the process for me. Coming out was easy, but in reinstalling it didn’t offer me that satisfying click or settled feel. When it and the AC socket looked and felt firm and stable, I called it good enough and judged, like others, that the clip was really unnecessary. Everything lined up, so I felt ok about it. That AC plug is so tight that when I went to pull it out before starting the repair, I momentarily wondered if it was built in, so when I was able to plug it back in firmly and nothing was loose, I felt good about it.
Guide was excellent; took all the anxiety out of the process for me. Didn’t break anything, thanks to the warnings.
I wasn’t able to use the plastic opening tools. I used a razor scraper to open the gap enough to get the putty knife in there. I bent up the first side a bit—it’ll never quite close right again—but it just back in my car as my car stereo hard drive. The rest came open pretty quickly once I worked in the putty knife. The putty knife was just a hardware store blade—nothing special. Reconnecting the battery cable was a bit tricky; I used a pair of dull tweezers. Now it’s back together and working, though not quite as pretty; not as hard as I expected.