Okay what's the worst to happen while opening, if one is moderately cautious and don't rip off the flex cables? I am in no way defending Apple's policies that

Okay what's the worst to happen while opening, if one is moderately cautious and don't rip off the flex cables? I am in no way defending Apple's policies that are openly hostile to repair and maintenance, yet I'd expect most people to be able to open a Mac, if they read a guide/watch a video and they have the correct tools. I do maintain/install/repair most of stuff home - the worst offenders are the ones that consider epoxy a viable engineering tool for fastening. Macs at least don't do that... yet. Also they don't contain built-in mechanical points of failure (printers are notoriously bad when it comes to weak springs and certain plastic gears; I don't consider having too short flex cable 'mechanical')