i hear that!
I actually have some 50mm lowering springs and dampers, my dad said the dampers are leaking oil and the bushes are fooked so i have to get new bushes and get the dampers re sealed (can some one do that?) before i put them on ... will gave to get that done as a matter of urgency ... i should think it would be freezing driving at those altitudes 
Dampers generally cannot be overhauled. If the car was 50 years old when things were built properly, then maybe.
Depending on the type of dampers you have, it may be possible to buy new inserts for the dampers.