2004 Corolla driver's side a/c vent control dial

My daughter just showed me as she was leaving our home that the round dial on her driver's side air vent (a/c vent) was partially missing. This is the dial that opens or closes the vent. Perhaps it got brittle and somewhat broke off???? If I wanted to replace it, is this a difficult job? I mean do I have to take a lot of things off or apart to get to that dial? The dial is round and it's edge is what you slide up or down to open or close that vent.

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Without looking at the vent, I would guess that the dial is part of the vent register assembly and that you would have to replace the register as an assembly. The register assembly is probably held in place with clips and pops out. If you get the replacement piece, you can probably tell how it is held in place.