Protection Training

Question
I have a 3 month old G/S female.  I am doing the obedience training myself and she has mastered the sit, stay, and down commands. I am using the "The Art Of Raising A Puppy" as my guide. I want to know if I need to have her trained for home protection or will it just be natural for her to do so?  
I have 2 small papillons that alert me whenever someone comes up the driveway so would my G/S learn from them?   She has started giving low warning barks when the ups man is making a delivery. We live in the country on 70 acres and when my husband is out of town, I would feel so much safer with a brave German Shepherd watching over us.

Also, my vet will not spay my G/S until she is 6 months old.  Do you think it should be done sooner than that?  She is also removing her dew claws when going in to be be spayed.

Answer
I frequently suggest that book.  I like its strong emphasis on leadership.  You want the dog to take its clue from you, so it allows the UPS man to make his deliveries.  If you go out and tell her to sit, she should quit barking and sit.  Going further in protection training is a very specialized area I can't help with.  Usually it isn't necessary, just the presence of a large dog is enough to make most undesirables to go elsewhere.  If you do feel you need more, find a good professional trainer with solid experience in the field.  

There is a movement toward spaying sooner, but I back your vet and the 6 months.  that is nearly always soon enough to avoid the mess and hassle of her first season.  Just don't put it off.