Couple of 2001 XG-300 problems, please help
 

The climate control temperature knob just stopped working. I thought I felt
it bind momentarily then start moving freeling again. After that though the
temperature control did not seem to work right at all. I could at first
adjust the knob somewhat and get heat out of it. Now it is very difficult
to get the temperature knob to respond at all. Could it be the Rheostat
that controls the temperature selection.

Also have been getting a musty smell in the car recently. I have never
changed the cabin filter in the car could that be the problem? Also how do
you change the cabin filter?

thanks in advance for any help you can give.
David