Isssues with G5 Heater box

pontiac
heating
g5

#1

I have a 2008 Pontiac G5. I have had issues with the heater on and off since I got the car in the summer of 2009. Basically, it just blew out hot air all the time. Sometimes it was real hot and made driving real uncomfortable. Late in the spring of 2010, I realized/found out the door that moves back and forth to allow heat out or cool air out was busted. If I went from heat to cold real fast on the knob it would send out cold air. Late in the spring it did it inconsistently before finally going back to sending out the hot air all the time. In July, I had the motor on the hater box replaced. My mechanic said the door not wanting to open had broken the motor. It again worked until about 1 month ago, when again it started to only blow out only hot air. I finally got it back to the shop this week. I was told that there was a bar (and can re-look up the exact part name later if need be) that was busted and he would need to replace the entire heater box. He told me that would cost $1200 as the dashboard needs to be taken off. He said he could try and fix the bar with epoxy for 100 bucks. I went with the later option as I am not sure I can or want to spend 1200 dollars. I just did at 9 hour drive after getting it fixed and now I just get cold air which was an issue as my window fogged up. Is there anyway of fixing my issue without shelling out the $1200? Should it really cost that much to replace my heater box? Thanks for the help in advanced.