2001 Dodge Stratus Blown Gasket Head

We started having trouble getting both our heater and air conditioner to work properly consistently so we took it into the shop to get it fixed, as we had the money and it was getting rather annoying. They said that our thermostat housing had gone bad and charged us $400 to replace it. The next day, as we were driving home from school, all of a sudden the engine started overheating, and within about a minute all the bells and whistles had gone off. We took it back into the shop and they kept it for about 6 weeks, then gave it back, saying they didn't know what was wrong and that we would have to take it somewhere else, it was still overheating badly. A friend mechanic of mine said that they hadn't properly bled the system and that an air bubble had probably caused the car to overheat the first time. He bled the system, but it continued to overheat. Finally, we took it to a dealer, who promptly identified a blown head gasket, which would cost about $1400 in labor alone to fix.
I and a few others think that the shop we took it to improperly bled the system when they replaced the thermostat housing they improperly bled the system, which left an air bubble and caused the car to overheat, which resulted in the blown head gasket. I was wondering if my thoughts could be correct, as it had never before overheated until the housing was replaced. Do you think there is a way we could get the shop to pay for the damages, or are we on our own? Any help or opinions on our options would be greatly appreciated.
Thank you.