DB- I've trained all kinds of dogs - pointers, flushers, retreivers. So, while I have my favorites, I too jump breeds. Right now, I'm buying a couple of European breeds. Wanna see what they've got to offer.
GWP is a good, versatile dog. It is obvious to me that you possess some intelligence, so head over to your neighborhood library and bone-up on the breed. I am reluctant to say to potential buyers of a particular breed: "Watch out for XXP dogs, they've had lots of temperment problems . . . Be careful when buying XXY dogs because they've got a high incidence of hip dysplasia and retinal atrophy . . . XXZ dogs seem to have lost their hunting instincts as there is too much show blood in them now" or any other type of caveats that might cause a buyer to have a mindset about a particular breed (only later to have their self-fulfilling prophecy come true).
GWPs can be trained to do whatever you want them to do -- track like bloodhounds if you so desire, be used exclusively as duck dogs, be used as combo upland bird pointer/waterfowl retriever, and even to run rabbits. So, go get one and "see fer yerself" as the saying goes. You won't be disappointed.
A "general hunting dog" book or two will get you started. The hunting dog magazines are full of well bred dogs in the classifieds. Utilize what the AKC has to say. And of course, there are breed specialty groups that have forums on the net, and local chapters near your hometown. The Verein Deutsch Drahthaar Club has an informative website (but I can't off-hand think of their actual name, do a google "drahthaar" search).
General Books - Gun Dog Breeds by Charles Fergus, Practical Hunter's Dog Book by John Falk (might be out of print, but othe Falk books are available). And don't forget to read past articles that have appeared in Gun Dog magazine on the breed like the June/July 2003 issue, "The Drahthaar" by Jerry Thoms.