I removed the external cover using a small flat blade screwdriver as I didn't have a tool for the security torx screws. I discharged the capacitor. After reading online the most probably cause of my problem was the Magnetron. I tested the unit with an ohm meter by checking between the leads and also to ground. While the Magnetron tested good with this method I decided to replace it anyway (shot in the dark). A new part came from AppliancePartsPro within 2 days (they are awesome) and after putting in the new part, viola, microwave was working again.