Congratulations! Your wife will love having a protective companion around when you are gone.
Petsmart - I think it depends on the store. I've met some very good trainers at our local store. And it could never hurt getting your puppy socialized in a safe place. I would recommend finding three trainers in your area. Go and sit and watch a class now, so how you like. Will you be bored? Are the dogs learning anything? Are there any GSDs there?
If you feel comfortable posting your location, there may be someone on the website that can refer you to a good trainer.