I can manually move it with a little wrench or from inside -- can spin each impeller and rotate the whole gizmo, BUT when I turn on the switch, there is an electrical hum but no functioning. It is an Emerson E100, maybe 15 years old?
Sounds like a motor problem. After 15 years, the blades are probably getting dull anyways and a new unit is in order. Emerson is the manufacturer of Insinkerator disposals so changing it out should not be a problem.
if you have never made a mistake, you probably haven't done much.