Open the cabinet above the Spacemaker and unplug the microwave from the wall.
Instruct your assistant to hold the microwave up so that when you remove the support screws, the machine won't tilt forward or fall down.
Locate and remove the mounting screws securing the microwave to the wall. A screw will be located on either side of the machine. Once the second screw is removed, grab the bottom of the microwave and hold until the assistant adjusts to support the machine from the bottom.
Lift the microwave up until it separates from the mounting plate and pull away from the cabinet. While you do this, have your assistant feed the power cable through the hole in the bottom of the cabinet to ensure it doesn't snag. Once this is done, you're free to install a new microwave or do whatever is needed with the machine you've just removed.