Guys:
I'm resurrecting this excellent thread to see if others encountered what I did.
I can't quite gain access to the switch area from behind..because there is a metal plate..aproximately triangular in shape in the under-corner of the dash... that is firmly attached that covers any possible way to get to the switch. The plate mounts a pull-cable for the gas tank or trunk release. I'm surprised I don't see the plate in George's posts ( see first underdash photo by George).
Do you then take out the switch from the frontside cockpit panel, instead?
---Wil Ferch