I would recommend that you post a request on the Repairs@Whitegoods module. You are quite likely to find a company that will help you.
I would urge great caution when working on Microwave Ovens. There are components inside that store energy for a long period of time (when switched-off)
Also, if you start opening the oven covers, you will need a means of measuring microwave oven leakage.
Unless you have the know-how and equipment, please contact an apporopriately qualified individual through the Repairs@ module.