[Leica] What are the limits of Lens Repairs?

[RedDrake@aol.com]

I occasionally find some neat lenses with various ... ahhh....difficulties
and sometimes buy them for the entertainment value, if they're
cheap enough. I know that some defects in a lens are repairable, and
some aren't (or at least not practically).

Based on my admittedly limited experience:

Doable:  fix stiff aperture ring, smooth/relubricate focusing
helical, cosmetically clean outside, fix rangefinder cam,
repair aperture blades, and cleaning out fungus (though
the damage might already be done)

Maybe: replace a part in the lens -- easy IF the repair place
can get the parts, impossible otherwise.

Difficult or Impossible (I'd like to know how bad these are):
Repolishing elements, recoating elements, recementing
elements

I would like to know at a relatively short think whether
a lens is "saveable" or not. You know it's not always
economically feasible, but I like saving an old lens from
entropy.