As others have said, contact the breeder. The good breeders will want to know if there are genetic problems in lines they are breeding. Even though there is no guarantee, the breeder may offer to do something about price on a new dog if the worst happens. However, if there was no guarantee and especially if the breeder doesn't seem to care, it's probably time to look for a different breeder.

Oh, and one thing about guarantees: Be sure to read the guarantee VERY carefully. There are a couple "breeders" in my breed that offer a 5 year guarantee. It sells dogs, but when you read it with a lawyer's eyes (the breeder does!), you realize it would be nearly impossible to get another dog or your money back.