This can probably be repaired by a qualified tech. At that age, it may also need to have the resin replaced. If it is the old type with a timer, I would trash it.
The newer ones use a flow meter to start the regeneration so they don't regenerate unless really needed. That saves a lot of salt and water. Sears markets one and also GE; the GE model is available at Home Depot. I installed one of the latter for a customer and was very impressed with the manual, as well as the unit.