I have a '95 850 T-5R and its rearview mirror developed annoying rattle. I'm not sure if your problem is noise or not. I got so agravated at my rearview mirror I was trying to find a no rattle spot when I popped it out of the house. The rearview was still connected, but it was dangling.

To get at the rearview mirror housing I popped down the plastic housing (I'm doing this from memory cause my car is in the shop atm...but that's another story) that the rearview goes into. This is also where the switch for the interior lights are. The plastic housing didn't come all the way out, but it exposed 2 torx screws. I remove those and then removed the plastic housing. Then the light assembly could dangle from its cords. This gives access to where the rearview is seated.

There are 2 larger torx screws that need to be removed and then I believe the rearview mirror will drop into your hands with the part the mirror arm goes into. The mirror arm is held in place by 2 metal rods the 'pinch the end of the rearview arm once it goes thru the hole of the metal plate that you just unscrewed. I think at this point it will be clear how the rearview stays in place in the housing. I seated the arm with the 2 metal rods nice and tight and the reassembled and the rattle was gone.

Hopefully this helps, and I apologize if the above is not entirely accurate since I am working from memory.