iFixit.com is where I ago to look at the Tear-Down guides and videos for my equipment. If something looks like a repair I feel comfortable with doing, I will get the parts and follow their instructions. When Apple changed to sealing the displays to the frame with adhesive tape for IP56+ dust and moisture resistance, I decided that was where I said “I’ll pay Apple the $89” for an iPhone battery replacement.
I had replaced the screen and battery on Foxbat, Jr.’s iPhone 5 which was a piece of cake compared to what it would have been on my iPhone 8. I traded in the 8 and got the iPhone 13 instead. It’s a balancing act, make the battery last long enough so it isn’t a Warranty issue, but not so long that the owner isn’t going to upgrade for five years.