I don't know if your familiar with the Yorkshire Terrier Club of America (YTCA), but they are they parent club of the AKC. They set the standard for Yorkshire Terriers. I know you are interested in breeding, and I think the best breeders belong to this club. There is a page of referrals, and you can find breeders in your state. These people would also make excellent mentors. For more information see:
Yorkshire Terrier Club of America