Whirlpool over the range microwave won't heat

Yesterday microwave was running and then we heard a pop - it kept running, but won’t heat/cook. All else works. What could this be and can we fix it ourselves?

I have a magic chef stove and the model # 6498VVD, 1 it takes 25 min plus to heat to over 400 degrees 2 do not receive error codes 3 takes twice as long to bake items bread normal 25 min takes 50 to 60 min 4 if you open oven door while baking temp drops 40 degrees real fast what do I need thanks lois