You are right. Internationally adopted babies aren't newborns, although some are delayed and seem younger than they are. And some birth defects are detected before you commit to a baby since they are older and those with problems have been weeded out, so to speak. But domestic is definitely the way to go if you want a newborn.
We did not do a domestic adoption, so I can't really advise you on that. I do know that you don't have to use a local agency or attorney, but I'll let others give you some direction and recommendations. Good luck! I'm going to enjoy sharing your progress!