The questions worth asking
Can I just put the same model back in?
You can, and sometimes that is right. But it is worth asking whether the original was sized for this valley in the first place. A unit that has regenerated constantly for years was usually too small from the start, and putting the same thing back repeats the problem.
Will a new unit use less salt?
A correctly sized unit regenerates less often than an undersized one, and that is where salt use drops. Whether yours improves depends on what you had. We will tell you which case you are in rather than promise a saving.
Do I need to replace the filter at the same time?
Only if you have one and it is due. Filtration and softening are separate products solving separate problems, and bundling them automatically is how water treatment quotes get inflated.