I need to replace my GE Spacemaker XL 1800 overhead microwave. How do I remove the old unit and find and install replacement unit?

Almost all new ones are wall hung on a bracket with top screws that come through the cabinet above. Open the cabinet and look for 2 large screws. If that is what you see, unplug the unit, have someone assist you by holding the MW up and remove the screws. When screws are out, slowly drop the front of the MW down and lift it off the bracket. Reverse depends on model you are installing. Last one I did required a new bracket (comes with MW) and the screw holes lined up. Template is provided with the MW for mounting the wall bracket.