You need water tests done to find out what equipment you need. I see a UV light, that is for Coliform bacteria. Air injection is usually for iron and/or H2S (sulfur). The softener is for hardness.
You can buy all the parts for a 5600 online for $100+/- and resin for $80-125 or so and repair the valve and replace the resin yourself. If resin is up in the valve, that can be cleaned out without the need of new parts in many cases.