Fan working intermittently, now smell burned wires

Kenmore Microwave model 253.5234903

This is an older microwave, the fan just started working intermittently. The other day my son cooked something in it for 10 minutes and we could smell like wires burning, terrible smell.

Is it worth fixing at this stage, can it even be fixed? It's still working but I'm afraid to use it.....my problem is that is is a large microwave and replacing one to fit the area it was in is going to be rough.

Thank you for your help.