Yes, it would be a pain-in-many-body-parts trying to attach/remove the wiring on the light-switch in-place.
I did it once.
I think that the last two/three times that I have rewired/wired light switches, I did the following:
Remove the old switch with wires still attached:
1. Disconnect battery cables
2. Remove light switch button rod
(as described in the Shop Manual).
3. Unscrew light switch "cap" (on the outer-part of the light switch).
4. Move/manipulate the light switch downward under the dash.
Disconnect (and later connect) leads with the switch hanging-down behind/beneath the dash.
Then, place the light switch back into its position under the dash.
Would someone who has done this recently please let us know if what I described above is possible (or, if my instructions are a "pipe dream").
Thanks,
Tim
