I was the same way before I got Jake, very nervous. I was scared I would do something wrong lol. But, things have gone really smooth for me. He was an "only child" so he didn't have siblings to miss. The breeder had weaned him away from his mom so he was used to not being with her all the time, and he was eating very well on his own. I think that's why he can play so well by himself if I'm busy.
Good idea sending a blanket with your scent. My breeder sent his favorite blankie home which had his mom's scent on it. Plus, I took one that she rubbed on his mommy so that it had her scent.
As for what to expect when you bring him home, he may not want to eat much at first because the transition is sometimes a little hard. You want to make sure you have things like cottage cheese, chicken, rice or chicken baby food so that you can put small amounts on his dog food to get him to eat. If you use chicken, just make sure to boil it (white meat). It's good to have Nutrical in case he doesn't eat and starts acting lethargic since these little babies can get hypoglycemic so easily. Make sure he drinks enough and if not, Pedialyte is always good to have on hand. Before trying any other foods though, you may want to try hand-feeding him his dog food. Sometimes they like that in the beginning. I hand-fed Jake for a couple days, then he started eating on his own. I free feed since he needs to eat often.
Potty training has been really easy for Jake so far. I've been using pee pads for now, and he does really well with those. He has only had a few accidents in the (almost) two weeks I've had him, which I think is excellent.
Make sure to have lots of toys and things he can chew on. My little one LOVES to play with his toys! Flossies and bully sticks are good to have so they have something to chew on.
Try not to worry too much, things will be fine. Just give him lots of attention and affection so that he will feel better about his new surroundings, and you will be amazed at how fast he bonds to you.
I have one question. You said your breeder brings him in the house sometimes. Where does he normally keep the puppies? Not outside, I hope.
Congratulations on your new baby, he will bring you lots of joy and will be so much fun for you!