Hyrdo---
German Shepherds are natural guard dogs. You can ask any GSD owner and I'm sure they'll tell you what awesome watch dogs they make (WITHOUT training). My neighbors had a long-haired GSD named Coke. He was very loyal and sweet, but a wonderful guard dog. I have a collie/shepherd mix. She has never set a paw in a training class, yet she has a strong bark, and guards well. A dog doesn't need to be trained to love and protect it's family.
The biggest problem I have with this is that German Shepherds already have a bad reputation. If your dog bites someone or shows any other aggressive behavior, there is a good chance the breed will have an even worse reputation, and that your dog will be euthanized.
German Shepherds are dogs that are loyal to their families, that want to protect them as much as possible. I read a story about a GSD breeder's male shepherd....their neighbor came over every Thursday to eat dinner, but this particular Thursday, he didn't knock on the door. Instead, he just came inside. The shepherd rushed to the door and placed his mouth over the man's hand. The dog owner came to the door and told the dog to release, which the dog did. He had held onto the hand hard enough that the man could not get loose, loose enough that he didn't puncture the skin.
Please, please, please, PLEASE rethink all this.
I would re-think having an "attack dog" trainer help you with any obedience training with your new pup. You need to go to PUPPY SCHOOL with any dog you get. Your dog needs to go to school to be socialized with ALL kinds of people and other dogs from the very beginning. You need to be the one to work with your dog so the dog develops respect and a loving relationship with you-it's loving owner!! I sure hope that you are not looking for an agressive breed so that you can have a guard dog. This is not necessary as people have said before, GSD's are plenty protective on their own. It is your job to help your dog control it's protective tendencies and know when they are appropriate, not encourage aggressive or attack behavior! Pleeeeeeeeeease re-think getting a puppy from a pet store. NO reputable breeder would ever choose this avenue. Most puppies that end up in pet stores are poor examples of their breed through carless breeding methods and lack of knowledge on the breeders part. They often have poor temperaments and are under socilaized...this can make for a dangerous situation with a GSD. A lot of times, the puppies that end up in the pet store are the last puppies left that no one would pick. There are reasons behind this. When I worked in the vet clinic, we saw so many puppies from pet stores that had parvo (a potentially fatal virus) and kennel cough, worms, malnutrition, you name it and they had it. I know this pet store claims to back you for one year, but trust me, you don't want to watch your pup go through one of these diseases...even if someone else is paying the bill. 
