You got your money out of the Mark 59 after 15 years and now that it broke and parts are not available say thanks and goodbye.

Consider replacing the Culligan with an industry standard softener from a local water treatment professional or from an online seller IF you're a DIYer.

Contemporary industry standard softeners are on demand design in stead of the old timer based units which makes them more efficient. Tech info is free for download and parts are available all over the place.

Here's what I'd do...

Get a water test from an independent lab. An independent lab has no agenda and won't be trying to sell you water treatment equipment. This is a MUST DO because without it everything is a guess. A quickie water test from Sears or a water softener company won't be as accurate (and possibly not as competent) as from a certified independent lab.

If you're on a water system the water utility can supply you with the specs of the water AS IT LEAVES their facility but that is not necessarily representative of the water conditions at your water meter.

Hit the Yellow Pages and call at least three local water treatment pros. Make sure you call at least one of the big dogs like Kinetico or Culligan for comparison and at least a couple independent pros. DON'T TELL THEM YOU HAD YOUR WATER TESTED.

Give each an opportunity to offer suggestions and provide you with a quote to meet your water treatment needs. IGNORE ANY THAT DON'T TEST YOUR WATER THEMSELVES as they can't speak intelligently to water treatment without knowing what needs to be treated.

Ask lots of questions. Softening the entire house or just the water heater (IMO a bad idea)? Warranty, parts & labor or just parts, how long and on exactly what? Install, permits required, licensed plumber? Routine maintenance and costs? Do they stock parts? Response time for emergency (water leak) calls? If they don't explain things to your satisfaction that is a good indicator of how you'll be treated after the sale.

After they've gone use your water test to compare with theirs. Are all your treatment needs being addressed?

Ask your neighbors if they have any water treatment experience. They might tell you who's good or who to avoid.

Come back here and post the specific recommendations and hardware components with the costs and we'll give you our opinions.

If you're a DIYer then you have other options but they must be discussed privately by email. But remember, when you do it yourself there's no one else to blame.