Lude Generation

I need to re-install the rear view mirror in my '99 lude. I've done it before so I should know how but I don't. The square plastic trim plate (which also houses the interior light) needs to come down but seems to be quite content just where it is. I own a garage full of power tools so removing it is not an insurmountable problem but I'd like to re-use it when I'm done.
TommyT