Couple of things

I just bought an '06 back in late august, switched from ford to chevy :D. Gotta love the car, the problem I'm having is when I turn on the a/c or the heater I get a strange musty smell. Is there an air filter I need to replace? Also even though it's been a short time the car already has about 10,400 miles in it.

One problem that gets me once in a while is that the car will tend to want to jump when I'm at a complete stop, only done it three times.

Also any other cobalt owners still have the problem with the cloth coming out of the door panels were you grab it to close it?

Last thing, if I want to remove the factory stereo to put in my own, how would I go as to removing the factory installed stereo?