should i try to fix or just buy a new one?

my ge microwave (model jes 2251sj02) stops after 10 seconds and does not heat. just recently it caused the circuit breaker to go off 2 or 3 times. i called ge and they said it was manufactured in nov 08 and if i didn't have a receipt(which i don't) it would not be covered. is it the magnetron tube and not worth fixing( i paid about $200 for it probably a year ago). or is it something simple and cheap that i could fix?? your help is appreciated. thanks, ken 480 985-9829