Hi and welcome to FixYa. I am Kelly.
Most of the time when the microwave is in use and just quits either the Power Diode or the capacitor has failed and blows the fuse inside the cabinet. (Yours is probably NOT blown.)
Location Item 19
Capacitor: (Location Item 20 above link)
Since you unplugged the unit before the thermal fuse blew you were very wise: (Item 28 of interior diagram)
With the unit unplugged and the chassis cover removed the fuse will be located at the end of the power cord lead in a fuse holder. The fuse is usually a 15A 250V slow-blo fuse. Just replacing the fuse will normally result in the fuse failing yet again.
STOP! Before going any further you must hold a well insulated screwdriver back on the handle and short across the High Voltage Capacitor at least 3 times!
Failure to do so could be the start of a very bad day in the form of a horrible shock.
Next you disconnect one side of the cap including the power diode wire. With an analog meter set on R x 1,000 read the Cap terminals watching for a jump. Reverse the meter leads on the terminals and watch for a jump EACH time you reverse the test leads on the CAP terminals.
No jump = bad cap.
Constant resistance across the cap = bad cap
Lastly you check the power diode with the meter on the same settings R X 1,000. One direction will read full continuity (ZERO) and reversing the leads will read infinity. (no reading)
If the diode reads open both ways = failed
If the diode reads (ZERO) both ways = failed
It must read continuity in ONE direction only.
After finding and replacing the failed component then you can change the fuse and test the microwave.
There is a very very remote possibility that a door switch has failed but given that your microwave failed while in use I seriously doubt you have a door switch problem.
As far as finding replacement parts for your microwave nearly every appliance parts store will have what you need if you walk in with the failed part in hand. Most of the time they will walk back and grab the part you need without even digging in the parts books.
These are the most common failures when a unit quits working while in use. Yes I believe your unit is repairble at a very reasonable cost.
Thanks for choosing FixYa.