Congrats!!!! I know how excited you are
You asked about socializing, I don't have any experience with singleton pups but I do have an older dog (non-yorkie) who was part of a litter and now due to my lack of knowledge isn't a very social dog. She tolerates her sister (my yorkie Chloe) but has fear of other dogs because I failed to socialize her. I would think that provided you take your little one out for walks and allow her to sniff and check out other (friendly) dogs she should be fine. Due to circumstances beyond my control my 1st dog didn't get the walks that she should have for learning social skills. Also Petsmart has doggie daycare if you don't have friends with dogs which will give your little girl the opportunity to develop her doggy social skills.
I wouldn't worry about her vet visits until she is home with you. You have said that your breeder is good so she will insure that your little girl gets the vet care needed. Once you take her home at 12+ weeks of age you need to take her to see your vet. All good breeders allow you a time period usually 72 hours to have your pup checked out for health issues and offer a 1 year health guarentee.
If she is your first yorkie I highly recommend reading about caring for your yorkie pup. There is great info here on YT. There are specific health concerns such as hypoglycemia that you need to be aware of prior to bringing baby home.
Again Congrats and please share some pics once you have some. We LOVE baby pictures
Tina21