Well, first off... Welcome to YT.
As for a stud dog.... I would think carefully about that and do a lot of research. If you do a search on here you will find a lot of valuable info.
You first need to make sure your male is a good representation of the yorkie breed. You can go to shows, look at photos and I would also suggest going to the YTCA.org website as it has a lot of good info as well. It takes a lot more than just throwing a couple of dogs together. You have to be knowledgeable about your lines as well as educating yourself about breeding in general. Also, stud dogs tend to mark a lot and that can be a difficult thing to deal with so there are a lot of negatives you will have to consider as well. As for testing, yes, again if you do a search, you will find some good threads on here that will give you some ideas about what to expect although costs really range a lot depending on where you live.
Good luck!
Here's a thread you can check out that is asking some of the same questions you are:
http://www.yorkietalk.com/forums/sho...d.php?t=118579