I have a 10 year old male GSD from a German (polizei) line (no slope in the back--it goes horizontal, no squat-like appearance, 120#)
1. good with cats? He loves them. too much. and loves the litter box also or any other place a cat may leave a "snack". In the younger years the dog and cat chased each other around and around and around the house, sometimes all night long. But they also had cuddle time too.
2. good with young children? Once I retrained a bit, but in the early years I kept him away from kids since he tended to match them in temperament and uh, herded them or got too excited and barky (scary bark, even when friendlylike) around them and I could never find training ground with little ones that I felt safe in, so I had to do a lot of dominance work when he was an old man with my dd.....I think it was easier because his puppy years were long gone and he had more patience. GSDs are very "talky" so it can be noisy with little ones napping.
3. how to find a good breeder, and what to look for in a pup/breeder? I found a farmer who was not really a breeder primarily as all the breeders were advertising things I just didn't want in a dog. I chose my dog because he was the most fearless and curious of the litter--and he came right to me.
4. what types of q's to ask breeder? I'd want the parents on site to take a look at--other than that they'd be individual questions for you as to the type of the breed you're looking for.
5. difference between male and female(we have a female cat-would that make a difference?) I haven't really noticed much difference, although at the dog park it seems most of the males are the "police officers" with the other dogs.
6. what are common reasons you take them to the vet aside from regular check-up? Mine has a chronic illness--addison's disease, so up until his dx we spent a whole lot of money....overall (including all care) he has been an average of $500-600 per month. And of course needs special foods for his tricky tummy, also very common in GSDs. We got yeasty ears sometimes, and I have the nails trimmed as I've never been successful with that particular activity with him.
7. how often do they need to go to the groomer? I take him when he gets reeky--like once every 3-6 months. It depends on what you do with the dog--mine likes to go in the lake, and so during some summers there were more groomer visits, and he also attacked sprinklers and hoses (the water) as his own personal fun time. We use a furminator at home and that cuts down considerably on the hair, but it's a full vacuum every two days.
8. how many hours of exercise a day? During puppy years (until age 4) a LOT. a whole lot. He could hang at the dog park running for three hours, which is pretty much what I did for him for about two years. It was a big commitment but there were no kids then. most GSDs are very jump-up-y in the early years also---it's like their greeting, and in our case resulted in some training since I had no handle on it early on. I have friends who do an hour of biking a day with their GSDs, but it's never enough to wipe them out. In the later years, I've been able to get away with an hour or so of ball throwing with some rests in there as adequate exercise, as it was a PITA to take the buggy and dog--he just didn't get enough energy out going that slow.
9. good recommendations for training/info books? Mine did well with training classes--kept both our minds busy...while he was too big to compete in agility he loved it, did very very well with obedience, tracking, etc. I chose no schutzhund since my family's previously trained Schutzhund dog sometimes picked up ambiguous hand signals the family gave her and well, did training with people who didn't know they were doing it and took folks down at times. As silly as it may seem, I learned a lot from watching the dog whisperer--mostly in understanding dominance. And I also learned that trainers are, uh, not always knowledgeable about GSDs. And the gentle leader was crap with him.
I wouldn't go with a Shepherd for a first dog. I just wouldn't. They have about the longest "puppy" span of all dogs. They have to be closely supervised for longer in their youth than other dogs. They take such a highly trained owner (and I really wasn't one, and in the early days needed a lot more training myself than I got). I was too soft, too nice, too quiet with him--allowed too much in behavior, didn't know anything about dominance, just wanted a nice companion (which he really really is, and I'm grateful he was patient with me until I learned how to be a good owner). It has taken a lot of work to get the dog safe around dd, and it has paid off, but for the next dog I'm going to make some decisions differently about breed--not that I don't love GSDs, because I do! But I think next time a bit mellower for our family will be a priority. They tend towards dominance, especially with other dogs around. I've seen many highly trained humans with GSDs who defaulted to a dominant state naturally. They are extremely smart, so one false move--like giving a cookie when he so cutely asks for one---ends up in hell for you---because it only takes once for them to learn all kinds of naughty stuff. Mine learned how to work doorknobs, cabinets, the refrigerator, the accordian closet (for the shoes), you name it. They learn it. Diarrhea messes are common, even when they're not sickly, so I invested in a carpet cleaner for the rare times I've had carpet.
Some lifestyle changes I made since having a GSD that I would have never guessed before having him:
Took out all the carpet, never had fabric furniture (only leather), did a lot more laundry, got a bigger car, changed all the bed linen to things that don't attract hair, put in a 6-foot fence and a doggy door (in the older years), had a heck of a time finding rentals when we moved (considered a bully breed here). The pinch collar was a life saver, especially once I learned how to use it. Good luck in your choices! I hope you find a perfect family friend! If you're set on a GSD, maybe a tested adult would be a good match as your "training" dog.