2 problems with heat controls

I recently figured out that the actuator for controlling temp has gone bad. I've done research and have figured out where it is and how to fix it. While I was checking it out I noticed another broken piece. It is a piece of nylon that hooks into a metal arm that is connected to a diaphragm. I figure this is why I also cannot select where the air flow is going. I can't find any info on how to replace that part. It doesn't look as easy to get to as the actuator. I tried to pry the white nylon piece off but, no go. Any one done this before?

I took my temperature control actuator out and had it apart. Also had an electrician at my work check little motor inside. Everything seems fine. When I plug it in it goes to 1 side and will not go back when temp is changed at dial.
I'm thinking it may be something wrong with the dial now.
Any thoughts? If so, what's my next step. Is it easy to get behind dials?