Remove front dash cover, 2003 cavalier & rep ac control cable

Unfortunately, you can do it, but you will have to remove your entire dash in the process.  It's not really difficult, just time consuming.  You can remove the front dash cover by opening the doors and removing the covers on each side.  They are just clips that hold them on.  Take a flat screwdriver and carefully pry them off. You will then see screws on the side that you will need to unbolt, and I believe there are 2 more screws pointed upwards that you can get to if you open your glovebox.  After those screws are removed, remove the defroster grill in the middle of your dash.  There is just one screw to remove and it unclips.  Now you can pry the entire top part of the dashboard off.  There are more clips holding it on, so just be careful when you do it. After that, you will see a bunch of screws on the top side that you can unbolt and then you will be able to remove the front cover that sits behind your steering wheel. With these pieces out of the way, you can finally unbolt the front cover where your stereo is and get at whatever your trying to get at to fix your defroster/control knob.  
I had to go through all this when I installed my aftermarket stereo.
Good Luck!  

Reach under the dash from the back. take the cable off of the post.
straighten the wire (the wire feels like a spring. you will have to bend it opposite way plus some to straighten it). put back on post and use knob carefully

I would like to change my stereo too, did you take any pictures or have any other advice?