1. Pull out the plug before you hurt somebody
2. Google the make and model number and add wiring diagram to the search parameters. Something like this:
Magic Chef microwave mco160ub wiring diagram
Also Google using parts instead of wiring diagram and you will find lots of nice pictures to guide you to inspect it further like this
From your post you seem to be fairly handy with a screwdriver. Take it further apart and look for a burned spot; if it blows the circuit breaker for the outlet, it probably has a big black spot somewhere to give you a clue. You don't have much to lose at this point, it is already pretty worthless in its present condition.
There should be a fuse in the incoming electrical line inside the microwave cabinet; I'm surprised it has not blown before the breaker. Make sure nobody has bypassed the fuse.
There may be a large capacitor that could hold a charge and give you a shock. See upper diagram for an example. [you did unplug the microwave, didn't you?] if you see the capacitor you can short out the terminals on it with a screwdriver and it may make a fairly loud snap as it discharges; better the screwdriver than your finger.
The damage is probably on the control board. The control board may cost as much as a new microwave, but you'll have all the fun of taking it all apart to find out.