2001 Pontiac Grand Am body control module

My car started having problems after a weekend parked at the lake. I was ready to go home on Sunday, got in my car to start it, and the engine would turn over and occasionally start but then shut off immediately. After a couple tries I tried pumping gas and finally got it to take off. As I started driving away everything went haywire on my dash, speedometer needle and all other displays would drop to zero then a maybe a minute later would come back on. All the lights for service engine soon, security, lights, oil and such would come on and off again as well. I got my car home and then come Monday afternoon I wasn't able to start my car to drive to work. So I took it in to a mechanic, they ran a test with a computer and told me it was the body control module that had received water damage and that it would cost me $675 for replacement part and labor.I thought that was pretty spending so I checked around for part price and other mechanics' prices. I talked to a mechanic that my dad trusts and he said what they had told me was highly unusual which confirmed my belief as I couldn't imagine how my car could have gotten wet sitting in a drive way and it hadn't rained on the way down. We eventually took it to him to look at and as he suspected it was a loose wiring that was causing the problems and only charged me $25 as opposed to $675! Naturally I was pretty angry at the previous mechanic, so I called the mechanic out on his lie, the mechanic insisted they would never do such a thing and that there was in fact water damage when the mechanic looked at the bcm and that you can tell by the wiring turning green from contact w/ water. So I replied then why is my car working perfectly fine now and I haven't replaced the bcm? To which he replied that maybe the sun had dried the bcm of water.I still cried fowl and asked why that wasn't an option when I talked to you then when you wanted to replace the entire part, but I would like to get an honest expert opinion if you would. Sorry for the length of the writing but I felt the detail would give you a better sense of the picture. Thanks!