It may be a blown main fuse, or that one of the thermal fuses (cut-outs) has operated and not reset.
Take it to a competent service tech for a cost estimate (the cost may approach that of a new oven), but don't mess with the insides yourself. Microwaves have dangerous high voltage inside, possibly even when unplugged.
This is the fan motor: http://www.appliancepartspros.com/part_details.aspx?part_id=3034166
It can be lubricated with a parafin based oil (Zoom Spout turbine oil) of Union 76 turbine oil. It is best to remove the mounting screws for the motor bearings and then clean the motor shaft & bearing before lubrication. Do this on both sides of the motor. Most of them can be revived with proper cleaning and lubrication.
It sounds like the switch has fused shut, it may just need jiggling on and off a few times to free it, turn off the power before you try that. The switch can easily be checked by a competent engineer with a meter.
It does seem an unlikely coincidence though, are you sure you haven't twisted the lamp fitting as you inserted the lamp, thus shorting something? Check none of the fittings are loose or twisted