Maytag humming (but works)

Woke up one morning to find the circuit breaker tripped. Reset the breaker and the microwave was humming. Not as if it was running necessarily, but a somewhat loud steady hum. When we open the door the humming stops. When we close the door again the humming starts again. The display on the control panel hasn't worked for a couple years now. It displays for a few seconds at a time once a month or so, but the display seems to work a little more often now. The microwave works very well. It even seems as though it heats faster than it used to, but that could be my imagination. The light works. The moving glass tray works.

What is making it hum and is it something I can fix myself without getting electrocuted?