I found it easier to remove the door panel when I installed my mirrors.
1. Remove door handle (requires torx socket/driver).
2. Remove the two Phillips screws, ones located up near the mirror and the others behind the door handle.
3. Remove the two sheet metal screws at the bottom of the door panel.
4. Lift up on the door panel slightly to unhook it from the door just be careful of the wire harness's for the power windows/locks which you need to unplug.
5. Remove the wire harness and 3 nuts that hold on the mirror and the mirror is off.
6. Install is the reverse of removal.
It takes literally 5 minute's to remove the door panel and it's much easier too work with it out of the way.