Removing the glass from the rear view mirrors is easy.
With ignition on move side mirrors to the most inward position - there will now be a gap at the outer edge were you can insert a long thin flat screwdriver. Look for the circular plastic ring, there will be a plastic tab facing away from the mirror on the ring at 90 degrees to the ring. Put flat of screwdriver at edge of tab and gently pry/clip it off.
Refit by gently pressing it back in.