Congratulations on the new addition to your family and welcome to YorkieTalk.
Looking forward to seeing pictures of your "Yokie."
DvlshAngel gave you great advice. I just wanted to note that Biogroom is no longer carried at Petsmart. You will have to order it online unless you are lucky and have a pet specialty boutique near you that carries it. Biogroom will send free samples if you email their customer service a request through their website. I use their Fluffy Puppy shampoo, Oatmeal shampoo, and Silk Creme Rinse.
Definitely hold off on changing diet, but you don't need to wait a full year.