The other day I went to use the microwave (over the range) and the display was not lit up. The light and fan underneath would not cut on either. I figured a breaker may have tripped so I checked that and it was fine. About a half hour later, the display came back on. So I tried to use it and it sounded like it was straining (lower hum than usual) and a smell like something electrical was burning emanated. I turned it off and have not tried it since.

Is the heart of the unit bad and thus, time to toss it, or might this be a $75 part I can replace?