porknbeans brings up an excellent issue. In order to DNA test, you need a registery that you can apply to. My Llewellin sire and dam had to have DNA tested to register my pup. Is there any registry in the U.S. for your dogs? Are you willing to start one? Then with DNA testing all hounds will be as you want them to be. Plus, if the breed gains popularity, the name of your kennels becomes popular. With Llewellin, King kennels is popular. Every Llew can trace some of its ancestry to a King dog.

Anyways, I don't think you really need a lawyer. Just post a statement in your website, "...will replace with a puppy if a genetic defect is found and reported to us within one year of the date of sale.A statement signed from a qualified vet must accompany the claim..."