Cleaning and Stain Removal - HELP! soup on fire! Microwave stinks :(

So my mother in law decided to cook some soup in my fairly old GE microwave. She left on the lid which you are supposed to remove and it actually caught fire inside the microwave which is now very yellowed on the inside. My house smelled awful and still does 24 hours later even after airing it out pretty well. It smells better in the house but the microwave is BAD... Will it go away or should I replace the unit? Ive had baking soda sitting inside it for 24 hours with no luck. Its still very bad even with the door on it closed. Thanks for any input. I dont want to screw around with it if its never going to go away.

Place a cup of vinegar or lemon juice inside the microwave and heat as for a cup of tea and let set to steam and deodorize. Then, wipe dry. Discoloration is likely permanent. Put a pot of vinegar to boil on the stove to deodorize the kitchen.

HOw long does this take to know if it worked?

Well it helped somewhat but still not all gone. I think im gonna replace it.. its an orginal 1994 unit with no turn table and its small.. all the more reason to get a new one.. thanks for the info. I posted in another section becuase I thought I posted in the wrong area.. I think a moderator caught it and fixed it. Thanks again! Great site!