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Unfortunately when the unit sparks it means that the magnetron is arcing out to the wave guide. The magnetron at the very least will need to be ordered and replaced which is a $200 part. But if the arcing has sparked out and damaged the wave guide, then the microwave isn't even repairable and the entire microwave would need to be replaced to resolve the issue I'm sorry to say. As for the door panel looking foggy, that means moisture is inside the door and leaving the door open for awhile should allow it to dry out.
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