Self Repair?

I have had my iph12 for 5 years now. Updated ios 26 have no issues what so ever besides from random lag which is quite rare. The main problems i have right now are that, my battery health is in 73% and last around 2 hrs as Im a heavy user and back main camera is stuttering. I have a really serious privacy issues to send to the repair shop. So decided to take this in my own hands and to replace both in near future after i order them. Do you guys have any experience like this? How did it go? Any recommended stores i should buy my parts from?
Just really doing this cause, i want to squeeze this phone for another year or two. Until I upgrade to iphone 20 or something like that.