Every microwave I have ever installed has two mounting points. The first is a bracket that mounts on the wall and holds the bulk of the weight as the microwave rests on it. The second mounting point are two screws at the top.
You will need to remove the false bottom of the above cabinet if the two screws are not exposed there. Remove all the DirecTV stuff and take a good look. If you don't see the two screws towards the very front of the bottom, then look for staples or small finishin nails that would be holding the bottom in place.
Once the screws are removed, the unit should be able to tilt forward and lifted slightly to remove it from the wall bracket.
You should be able to download the specific install instuctions for your model from the Whirlpool site.
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