Cabin air control knob broken

[srm73]

Hi all. On my 2009 Yaris, the knob that controls the air into the cabin broke. I always have it set at the fresh air position. A few months ago, it stopped moving from that position to the air circulated option. Than some time ago it was very cold and I tried to force turn the knob thinking that It might get un stuck, but it seems like something broke inside. I could hear something breaking and falling on the bottom. Now the knob is completely free and doesn't seem to be working at all. Not sure what position is it on.

I am wondering if someone could guide me a bit in terms of how to fix it. That includes what portion of the panel to remove and what parts to replace. also how to remove that area.

Thanks in advanced everyone. Cheers.