It is my advice since youve never bred before you should wait until next heat and do as much research as you possibly can into how to breed, why to breed, when to breed and if you should breed.
Breeding these little things are not for the faint at heart and should not be taken lightly. Because of their size and structure and genetics many things can go wrong and as a novice even worse risk the health of your mom as well as her impending offspring.
that being said here are some websites you can visit to answer many of your questions ...second find yourself an experienced breeder in your area that is willing to mentor you which will certainly minimalize the risk for a first time breeder. Build a strong relationship with your vet, have him on call 24 hours before your whelping is due in case of emergency.
http://www.yorkietalk.com/forums/showthread.php?t=15504 http://www.debbiejensen.com/heat_cycle.html http://animalpetdoctor.homestead.com/Reproduction.html
wish you luck