Congratulations on your new baby!!! I bet that everyone will have a little trouble sleeping tonight because I'm sure you're counting the minutes until you go pick up your newest family member
Regarding his teeth, I agree with everyone that he would probably not have had a dental in a very long time.. and if from a puppy mill..there's a pretty good chance that he has never had one. So, I would definitely have your vet examine him and talk with them about having a dental cleaning done. But I would definitely want a vet to look at him to make sure there aren't any other underlying issues going on.
But again, CONGRATULATIONS!!! I am so excited for you and your family!!!