repair or replace?

I bought a house with a water conditioner that doesn't seem to be working. It is an OS-C0mb0 water with an INAQUA model 19400 control valve. It was installed about 13 years ago. Had the original installer/sales rep check it and told me the valve was not working properly. Asked him how much it would be to repair and he said about $2,600. Then said "because of its age, you should replace with new unit." Cost? $2,600. I have a well and the water hardness was tested as "7" in 1999. Does it make sense to repair? At what cost? This is the first time I've had a water softener so any help would be appreciated.