I had my water (softened and not softened) tested a few times before getting a new softener and a couple times after. I would think softener dealers should be able to test it for free. Sears will test it for free and maybe other places that sell softeners. For me they all agreed within a couple of grains.
But one of the "big box" stores that tested my water with two different kits (of the same type) and got different results, both being very different and way too high, compared to lower numbers a couple months earlier from the same place. I don't know what they did wrong, but the guy said the time of year and city pipes can make a big difference by adding hardness which I highly doubt. I was told by the city all the wells are blended.
You might consider going to two or three places to be sure and checking with your city as to what range you should expect.