I'm not in a rush to "fix" it and ruin a nice piece of TE.
I took mine apart, a different make, but very similar, at least one selector was very stiff.
Non metal inner rod goes through a center tube of a setting, if memory serves I had to push very hard to get the rod out.
It's also possible I had to use a hammer and punch, I doubt the sticky stuff was original.
I'd say that generally you can't ruin it without a hammer or something corrosive.
With bad luck you must file something, but it's better afterwards.
One problem is too much height difference between contacts, no contact or selector get stuck.
Other is burned surface, but it's pure metal, and selector finger can be adjusted, can't remember how the stud side is.
Worse it is if bottom contact plate or resistors have problems.
For grease I've not decided yet.
I guess I'll go with mineral, organic has a bad taste.
For the earlier thing,
it's Vdd <-> Vss.
Had to measure it.