Mike these things are usually screwed in, we have similar unit, etc. Al did a AB switch install, for the life of me I cannot remember where the screws are, but look under the radio cabinet (like under the cupboard and look UPPPPPPP) and look in the cupboards on both sides of the unit. Unscrew, and wiggle away and it should come out.
this is what ours switch looks like, finished, installed:
We did ours around July of 2004, you might be able to find a post about it by searching the archives???? I had the photo reduced, cannot find on our web pages, so, my ole tired out brain is telling me I posted here at MOC.
Good luck with your improvement.
Carol