I need a mechanic's advice!?

My fiance n I recently purchased a 2007 Toyota Camry from a used dealership. The second day we had it the gauges started messing up. When we would drive it the RPM gauge would start going all crazy, and the brake and airbag light would come on. Then a few days later the air conditioner would start to blow hot air out while this was happening. We took it back to the dealership we got it from and they tried to fix the problem but they couldnt. So they told us to take it to a Toyota dealership to see if they could figure it out. Toyota had it for going on 4 days and none of them could figure out the problem. So if anyone has had this problem before or a mechanic who might know what's wrong with it can you please help!?