Dealership Fraud

I have a 2006 Chevrolet Impala. Two weeks ago I could not start it, the power windows, door locks, remote trunk release, lights, horn and any and all other electrical parts would not work. I took it to my traditional mechanic and was told that my Body Control Module (BCM) might be bad and could need to be replaced. I was told that they could replace it but a GM dealership would need to complete the installation by programming it to the car. At this point I contacted a Chevrolet dealership and was told that I was better of having them install it and program it. This seemed like sound advice. I had my vehicle towed to the dealership and was told by the service manager that they could replace the BCM, but if that was not the problem I would be looking at additional charges. This seemed like good advice as well. He then told me that they could do a complete diagnosis and ascertain what the problem was. He quoted me a price of 140.00 for the diagnosis. He called me up later that day and told me that it was the BCM and they could replace it for 600.00 plus the 140.00 for the diagnosis. I agreed to have the work done. I then asked the service manager if he could inspect the vehicle, since I needed to get a new tag. He told me that they would not be able to inspect it until it had been driven a few days in order to sync the new BCM with the vehicle. The next day I went to the dealership to pick the vehicle up. I made a full payment for the diagnosis, parts and labor. The car seemed to run OK. Twelve days later my wife was out at night and tried to start the vehicle and it would not start. The lights would not work, the car would not start, power windows and door locks would not work and there was no evidence of any electrical components working. These were the very same problems that we were experiencing with the vehicle when we were told that it needed a BCM in order for correction. I went to the dealership that had installed the BCM and told them that the vehicle was experiencing the very same and exact problems that they had stated were contributed to a bad Body Control Module, (BCM), which they had replaced. The service manager said that he would have the vehicle towed to the dealership for repair. Later that afternoon the vehicle was towed. The following day we received a call from a different service manager. He informed us that the vehicle needed to have the positive battery cable replaced and with the tow fee it would cost around 550.00. He spoke with my wife who conveyed this information to me. I called this individual and he told me the same thing. I then asked him this question: If the vehicle was doing the exact same thing as it was before the BCM was replaced, how could they be sure that the problem was the BCM and not a bad positive battery cable all along. He told me that he was basing his diagnosis on what his service technician had told him. Again I asked him if it was possible that the BCM was once again failing, given the fact they the problems were exactly the same. He told me that when the vehicle was previously diagnosed that it had been determined that the BCM was bad. I requested all receipts and documentation concerning the replacement of the BCM that the dealership had done twelve days earlier. I was denied this information. I paid the dealership 120.00 for the tow fee and drove the vehicle to another mechanic, who told me that the battery cables needed to be replaced. I purchase the battery cables for a local auto parts store for about a 100.00 and had them installed for around 80.00. This fixed the problem. Due to the conversations that I had with the second service manager, his answers, body language and what is reasonable, I believe that the battery cables may have been the problem all along. I further believe that the dealership did not replace the BCM, but the vehicle cranked once they were working on it. I based this belief on the following: After the BCM was replaced and the vehicle was driven for a few days, when we tried to start it, there would sometimes be a click and everything would go dead; dashboard lights, interior lights and other electrical components. Upon a second or third try the vehicle would then start. When I had the vehicle towed to the dealership, the first service manager told me that once the tow truck arrived and they attempted to crank the vehicle it started. It is my belief that after a period of time passed or due to the vehicle being jolted or moved around the faulty cable made contact and that is what allowed for startup of the car. I do not believe that the dealership ever replaced the BCM. I took the cover off of the dash underneath where the BCM is located and the unit did not look new. This is my question. Is there any way to confirm whether or not the BCM that is now in the vehicle is the one that was originally installed, whether or not it was recently installed, when it was purchased, when it was synced to the vehicle or what is the age of it? I sincerely believe that I may have been defrauded by the dealership in which I paid almost a thousand dollars to fix my car. I further believe that they placed my wife's safety in jeopardy by not being honest about the repairs that they claimed to have done. I would appreciate any and all assistance, comments, and opinions and/or shared similar experiences that anyone could offer. My sincere gratitude is offered in advance.