I'd give it a 3/10 repairability score, since every major component (CPU/RAM/SSD) is soldered and unreplaceable/not upgradeable. At least it's easy to open.

You have to remove the five small screws on the lower edge of the iMac to remove a strange bracket or something, like the 21.5” 2012->… iMacs

The only thing that fan is doing is moving a (tiny) bit of air indirectly across the logic board and the heatsink. Or at least that is what I think it does. As there is no direct heat conduction from logic board to case, the fan isn’t there to cool the case, that’s for sure.

I fixed it right now!

Why is everithing so yellow? Was it put outside?