I had to replace the manual heat-AC fan-switch assy in a friend's '84 Euro W123 300D. The attached cable had gotten so stiff that the PO broke the end of the pot-metal shaft that held the fan-knob.
Then the PO tried to fix it and trashed the faceplate, shattered the plastic cups that held the retaining-nuts, and split the 3-hole plastic mounting-panel. So my friend searched eBay and found a complete manual W123 control set, with all the switches, knobs & hardware.
Unfortunately, the 3-hole mounting panel, which is normally part of the heater-AC box, wasn't included with the control-set.

Because the 3-hole panel was only split across one of the holes. I decided to try repairs without pulling the center-console. I was able to pry the split panel out just far enough to replace the switch. While I was in there, I disconnected the cable at the bead-coupling and where it attached to a lever behind the glovebox. Then I squirted some ATF in the cable-ends and worked it back & forth by hand until it unstuck. When I installed and tightened-down the replacement faceplate, it pinned the split panel back together.

Still, for me this was long tedious job.
Depending on how badly yours is damaged, it may be better to just remove the center console first.

Happy Motoring, Mark

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DrDKW