well lets see, where to start??? some of this you may already know, hopefully some of it will be new info that will help you. 1st off to answer your 1st question...price depends on what you are looking for. do you want american showlines? (I suggest avoiding those), german showlines, german workling lines, czech lines? heres one site that shows some of the different types
http://www.nwk9.com/type_comparison.htm
if you are interested in doing schutzhund, herding, agility, etc I would recommend working lines. if you want to show, showlines of course. just a family dog? Id recommend a breeder who uses european lines, wether working or show. american line dogs have smaller bone structure, smaller heads, and can barely hold their butts off the ground. they are a lot more prone to genetic health disorders.
for a well bred, health garaunteed pet quality puppy you should expect to pay between $500 and $1,200 dollars depending on the lines and breeder.
best time to take a puppy home is not before it is 9 weeks old. and when someone will be home to house train it and bond with it.
I have had gsd's my whole life and have been training them (and other breeds) for over 12 years. you are more than welcome to ask me any questions you want, on here, on the other site I pm'd you, or you can pm me. its hard to just start listing info about them, it would take forever and still wouldnt list it all, and I dont know what you already know.
and a big yard is deffinetly a must, but is this going to be an outside dog??? if so I HIGHLY recommend you stay away from gsd's. as an outside dog it will not be happy. it will be bored, hyper, dig and chew, it will find a way out of the fence, and it will be very difficult to control even on leash. not saying that to hurt you, or to sound like Im reading anything into your post. but there are a lot of people who get gsd's and other breeds, think it will be okay to keep them outside all the time, and then wonder why they cant control their dog. they are absolutely family dogs, and need to spend as much time as possible with the family. like I said, if you do a lot of research and ask a lot of questions you will not regret choosing a gsd.