i can see that theres a tab but i cant release it from the button im getting the wind shield replaced in a few weeks and also my mirror is a bit loose so id like to replace it too.

 

whoever is replacing the windshield will have the knowhow and tools to do it for you.

 

I just did my rear view yesterday. It was loose so I took it apart to fix it. There are three screws that hold the mirror on.

Look up and behind the mirror there is a visible Philips #2 screw. Loosen it and remove the mirror. There is a little metal clip with a threaded hole that may come off with the mirror. Don't lose it.
Then there is a square plate with 2 smaller Philips screws. (This is what was loose on my car). That plate screws to another little square that is glued to the glass. This is when the glass installers should be involved.

To re-install repeat those steps backwards. It is a little tricky to get the metal clip to stay in place. The curved/ hooked part of the clip points toward the front of the car. Make sure it is hooked in and seated correctly before tightening.