CONGRATS!!!! Rescue dogs are the best-and GSD -wonderful pick!!!
I'd advise that you take the dog to a vet within the first month or so that you get him, to get a baseline checkup. (phone around, search the internet if you don't have one already)-it's important to find a vet you like who will take the time to talk to you.
The checkup is a nice meet and greet as well-it's is a good thing-because then the dog's first trip there is not when he needs shots or painful procedures-so they aren't phobic when you take them in the future, and you vet has an idea what your dog is like healthy-and knows when he's sick.
This exam also gives you the chance to discuss your concerns with the vet (i.e. on rawhides, food choice etc. etc.).
The next step-find an obediance school/teacher you like. I think all dogs should go through one round of basic obediance-even if they know commands and are good dogs-it's good for both of you, and you can get feedback on what your doing, what you should do and how you work together
Congrats again! You'll have to post pictures when you get him home!