If you can get the piston and seals online and your husband is a handy guy there is absolutely no reason why he can not swap the parts out. Even if you have to buy the parts locally because Clack is no longer allowing it's stuff to be sold online, it will still cost way way less than $150.00 Changing or "rebuilding" the WS-1 is pretty easy with no special tools needed. After rebuilding the valve a water test needs to be done to determine if the resin bad is badly fouled. If there is no, or very little iron in your water, back to back regenerations should bring everything back to normal. If there is iron you will want to add super iron out to the brine tank and do back to back regen's and hope for the best. Sometimes with iron the resin can get so fouled that it will have to be replaced or removed and cleaned.
there is also a pretty good chance that the parts are OK and just need to be cleaned off and re-installed but the seals should be replaced at the same time anyway.