Softener has not been used for 6 years, do I need new resin?

I bought a Culligan Water Softener when I moved to Florida in 2007. I used it for 3 months and moved back to California. It has been stored but I am afraid the resin is dirty and a little of the resin may have been lost during the move. The tank looks about 1/3 full.
I called Culligan to get an estimate on an install and the tech said I should replace the resin. It was only used 3 months is it really necessary to replace the resin or can I just clean the resin once the softener is installed. Will the softener work correctly if the resin is a little low?