how to replace a built in microwave?

Not having been privileged to see this POS, I will guess that it is the Magnetron or the circuit board. If you pull the cover off, you might see some melted stuff. That would be a clue. New ones start well under $100.00. Are you sure that you want to fiddle with your broken one?

I didn't think this was possible without sending the microwave to the manufacturer. Sorry.

As it is a joint part, so it may take a year to cure. I know it pains a lot but try to bear the pain, still if it goes worse then go according to the doctor. Else consult with some other doctor.

Many people do not have the luxury (or the knowledge) to be able to prepare good meals every day. There are many people who favour recipes that you can prepare double the amount and keep some in the freezer to be eaten at a later date. For these people, having a microwave that can heat ready made ...

Thanks so much. You have been a big help.

It sounds to me that your microwave is fine but you should not use that china for microwaving. Sparks in a microwave generally appear when there is a metallic substance inside.