Hi!
I don't think GSD are harder to educate than Lab or other breeds of dog. I think, otherwise, that you have to now what you are doing. Educating a strong breed like GSD, Bulldog, Pittbull & als. isn't always easy. They are strong minded and you need "more" constancy, this is what I personnally think.
You seem to have time to take care of a dog, I think it's the most important. Plus, like you said, you are familiar to dogs.
As for choosing a dog between a shelter (rescuer) or a breeder....it all depend the way you see things. In both case, you will have to do researches on shelter/breeder/dog history.
It is pretty hard to know the history of a rescued dog...so you have to be prepared to any situation. I think it is more "louangeable" to adopte a recued dog

But maybe you will avoid few troubles with a breeders (by troubles, I mean health and being).
For sure, the GSD
IS a good dog, easy to traine, faithfull and playfull (full of energie!!) and I don't think you would make the wrong choice by choosing a GSD.
Good luck!