The resistor is a pretty easy change if thats what the issue is.
Just be glad its not the blend door actuator for the hot/cold. I have the dual zone climate control on my 2006 Silverado and i had to change the passenger side hot/cold blend door actuator this summer. I had hot air on the passenger side only, no ac(drivers side was fine). It required some serious dash surgery to remove and replace it. Radio, airbag, onstar control box etc all had to come out and the top of the dash removed to get to it and i still had to work blindly by feel to get it done( its under the defrost ducting). All told a two hour job, i imagine a dealer would have charged at least a grand to do it.