Hmm, couple months ago I repaired a GE Microwave (30" over-the-counter model, impossible to find another brand that fits the opening). Lots of warnings on the circuit diagram tucked away on the front of the chassis about discharging the 2KV 1.1 microfarad capacitor, despite the fact that it includes a discharging diode shunted across it. So I took an ohmmeter lead and shorted across the terminals just to make sure.
Anyway, first I replaced the magnetron since that is the part most likely to fail as well as cheapest, then the capacitor and diode (next cheapest), and finally the transformer which did the trick and also most expensive. Never, ever order replacement parts from GE as they are easily twice to 3x as expensive. While the Samsung-made magnetron part had a 10-year warranty, GE refused to ship me a new one as it was not "customer repairable" according to their policy, and so it would have cost $100 just to send out a repairman to diagnose the problem, order the part and then another $100 for the followup visit plus the time required by the actual repair. In short, anywhere from $250 to $400 for labor only. GE wanted $179 for the magnetron; I found the exact same Samsung part on the web for $49. Unfortunately I don't have the necessary diagnostic equipment so I had to resort to the old plug & chug replacement routine, but still my total cost was less than the price of two visits by a repairman, plus now I have all new parts so the microwave should last another 5 years or so..
I will avoid buying GE appliances in the future as they have a lousy rep on the web for the last decade or so..