I have pics but can't load the format.
The glass is glued/silastic'd to a plastic holder, the holder is held to the sealed drive motor by a gimble or trundle (snaps into place).
This allowes up/down & left/right pivot movement. There are also two (2) threaded posts that slot into two (2) holes in the motor assy.
When you push them in, they ratchet down like the brake switch on a holden or C3. The motor engages the threads to drive it in or out.
The motor assy is secured by three screws - and it appears these come loose, re-tighten c/w threadlock.
Yes - you need to be carefull, I pulled the mirror down at the top so I could get fingers or a flat paint scrapper into the gap and gently tug on it and it will snap one end of the trundle (cross thingy) out of its holder, then work your way around ...... gently.
The mirror if firmly glued to the plastic holder, should not break, but you need to keep any force flat, because the plastic will bend and the glass wont.
Oh! I did not mention the heat pad (if fitted) is wired and if not tampered with will not have any connectors in its wires, if there are its a dead giveaway that some one has already been there. The wires are connected flimsily to the heat pad, the mirror can hang from them while you do the screws, but be carefull, they easily pull away from the heat pad, which after 30 years is lucky if still working and notcorroded out.
Once apart the above will become clear, snap back together after the threaded pins are seated, I used a thick soft pad between my hand and the glass when snapping the trundle back together - can take a few goes since it has 2 places to snap into.