o/d switch repair?

[jim.wallace@netscape.ca]

One of the switches on the top of the gear selector cover that allows the
overdrive to function is flaky. I took out a shim and it makes better
contact, but not a nice consistent low resistance. Sometimes a few ohms,
sometimes a few hundred ohms, sometimes wandering as I watch.
Can the switches be taken apart and contacts cleaned? If so, any gotchas
before I dive in and bust something?
Thanks,
Jim
60 3a, 4A o/d