Microwave turns on when door is open

My LG model # LRM2060ST microwave just recently began turning on the fan and light, as well as spinning the turntable whenever I open the door. Otherwise it works properly.
Any ideas?

One or more of your door switches are defective.

Is there a way to pinpoint which is defective?
Is the microwave worth fixing?
What are the part #'s so I can purchase them?
How do I replace them?