(New to the Community Forum… hi!)
I recently installed both the FP3+ Top Module and Camera Module in my FP3, and can confirm much of the advice given in this thread.
1st, Have the proper tools. The screwdriver supplied with the FP3 is a PITA. In anticipation of some more major work on some other equipment, I got an Pro Tech Toolkit from iFixIt, https://eustore.ifixit.com/products/pro-tech-toolkit/145307 (whilst recommended, this post is NOT an ad for iFixIt!). The iFixIt screwdriver works much much better than Fairphone’s, the magnetic pad helps to prevent loosing screws, the Opening Picks helped to remove the Display Module, the “Spudger” worked great for removing the connectors, and the Reverse Tweezers came in handy when trying to free a recalcitrant screw. I wore latex gloves. Also, ensure you have a clean level properly-illuminated workspace.
2nd, Read/Watch the instructions all the way through BEFORE proceeding.
3rd, Remember to power the Fairphone OFF!
4th, Be Careful! Do NOT “force” anything. GENTLY unscrew, GENTLY pry, GENTLY lift, etc. Here’s where using an Opening Pick to pry the Display Module free helped, it was much easier (more gentle) than trying to do it by hand as FairPhone suggests.
5th, For both the Top Module and Camera Module, make sure to remove the protective blue covering over the lens on the new (FP3+) units.
6th, I had no problems at all replacing the Top Module.
7th, Like others in this thread, I had problems with the Camera Module, including accidentally loosening the hidden end of the cable. Unlike others, I’ve not been able to get the new (FP3+) Camera Module to work (more on this below), BUT the old (FP3) Camera Module can be reinstalled and works fine. (Huh?)
8th, You don’t need to completely reassemble the FP3 to test it. Just make sure the Display Module is firmly reattached. I found it useful to screw it down with five screws, the most important one being the one above the SIM/SD slots next to the battery well (this seems to ensure the Display Module is making a proper connection to the main unit). The other four screws are those in the four corners (one screw per corner).
*#*#66#*#* diagnostics are incredibly useful. They confirmed the new Top Module is working, but that (for me) the new Camera Module (including the flash LED) is not working (but that the old Camera Module, when reinserted, is still working).
Despite having the Camera Module cable problem mentioned by others, which I fixed by using the iFixIt “Spudger” (as I now recall), my new FP3+ module simply doesn’t work. The before-mentioned …66… diagnostics report an error (the module (camera and LED) isn’t detected). I can reinstall the old FP3 module and it does work. I’ve done this twice now, and so am currently concluding I was sent a defective FP3+ Camera Module. (I will be contacting Fairphone Support about this.)
Not sure if this rambling helps anyone. My own top advice: Proper tools used gently on a level workspace!
EDIT 1: Fix an offering to Tpyos, teh deity of typos.
EDIT 2: Sorry, forgot to mention: 10th, Update to Android 10 (mandatory!).
EDIT 3: Clarify which five screws (when testing (8th)).