Here are your parts, includes a wiring diagram
Model MDE9557AYW
If the hum is coming from the motor, it may have bit the dust.
This may take two people
First try rotating the drum by hand, it should turn fairly easily.
Open the door
Hold the door switch closed
Push the start button while rotating the drum in the correct direction
Watch your knuckles in case it starts up
If the dryer starts up, odds are high that the motor is shot re: one of the windings has burned out.
It sounds like your earlier high heat problem may have been due to a grounded element. Could be it is either broken or it has sagged and touched the case. Check it either visually or with a meter.