Yorkie's are wonderful! I'm so in love with my Bella!
As far as costs for vaccinations it probably varies depending on where you live, I would call some local vets and see what they charge. As far as sex, I'm partial to females because I never want to have to deal with a male dog marking his territory.
But, I've always had females (have 2 now) so I really don't have much experiance dealing with a male dog. Good luck in your search for your new baby!