It depends on where you live. Grooming you can do at home. All you need is brushes, comb, dog shampoo and nail trimmer or a Dremel. For a GSD mix, I'd suggest a good rubber curry comb type brush, either one like what they use on horses or a Zoom Groom, and a bristle brush. I like the metal combs with teeth of two different widths for getting the under coat out(sometimes called "Greyhound combs"). Shedding blades and Furmantor type things break the coat.
Vet- It depends on where you are. In Novemeber I paid $160 for our Lab's annual check up, vaccination, Interceptor (heartworm preventative), and anti-biotic cream because he had an ear infection. That's fairly inexpesive for NJ. The best suggestion I can give you on that is to talk to some other dog owners in your area and ask them about costs.
Food- again, it depends. Not just on where you live, but what you're feeding. Our Lab's food runs a little over $2/pound, but he has allergies, so is on a limited ingredient food.