Car rip off?

My car began stalling out on me last thursday, it is a 2000 chevy impala. I went to townsend chevrolet and they told me that it was my body control module that was causing this and that it would cost me 520.00 to have this installed in my car. That was too high for me so after I paid them 100.00 for "diagnosing" my car i went to Willis Chevrolet with the diagnostic sheet that Townsend brothers had provided. So Willis had installed the body control module for 363.00. I paid them and no later than five minutes after I had left the dealership the car stalled again. So the car was misdiagnosed by Townsend Chevrolet and I am screwed out of 363.00 or am I? I want to know is there anyway that I can make Townsend pay me back for misdiagnosing my car. They had only agreed to pay me back for the 100.00 diagnostic fee which is unbelievable! What should I do I don't have money to throw around or a car to drive to school and work.