Pray that the 40 year old plastic is up to it! I didn't chance it, and removed the panel to get to the switch on one of my cars. My panel was just as damaged by water from a leaky windshield seal.

The under dash "covering" and floor mat must be out, and then you can move that side covering panel up and forward to get it out. It's got to come out of some little clips that are in with the pinch welt (two I think), and there might be one or two on the lower edge tied in with that grey plastic covering. In your panel pic you can just see the tip of one of those clips on the vertical edge, just up from the warped panel edge at the bottom. You can see the indent left by it in the vinyl covering that's shrunk back. Be glad you don't have speakers down there! Makes the panels more fragile.

If you can coax the switch out that would be a much simpler path. Or, if you want to make some new panels go ahead and remove the old ones. It's tricky to get water damaged ones back in, with the vinyl peeling and brittle cardboard. I've wanted to make new ones but haven't so far. Other fish to fry!