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I think the question is how to swap in a new light switch. Is that the question?

. . . . So I reiterate: Replaceable electrical items always have a "service loop" (extra wire length to hang down) for access without crawling on your back. . . . This is a very easy procedure. You simply replace one wire at a time so as not to get confused....or make a drawing..........or whatever.

Chances are that there is enough slack (service loop). Just untangle/manipulate/stretch/hang where possible and swap the wires. Should be able to do it sitting in the seat or leaning in on the floor.
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yes - nicely stated

I dimly recall that I learned to wear tight, strong, flexible gloves - to keep from cutting my fingers/hands on sharp edges of metal under the dash?