My speakers on the driver door, passenger door and behind the rear seats have stopped working. Is this a simple fix or something more complicated?

 

What happens when you turn the radio back on?

 

hahaha...

 

amp perhaps

 

My amp caused one of my rear speakers not to work. If you can get access to the speaker wires behind the speaker, you can jump it with 2 speaker wires and hook it up to a spare speaker. Then that way you'll know if the speakers are getting powered.
Another thing to try is using the wiring diagram and the amp to see if there is continuity in the affected area.