Wow...congratulations grandma....
Is this your first litter? Do you have a mentor....an experienced breeder to be there during the whelping to help you?
I am sure you are excited and I am not a breeder but there is a ton of info here if you search the threads. I know you want to be as prepared as possible so I would say read read read and then read some more and aks your mentor lots of questions.
If you don't have a mentor, I would try to find a local reputable yorkie breeder who would be willing to help you out. there is a lot to know and I think you will be relieved if you have someone to help you through this.