A GSP is a great dog for hunting upland game (both birds and furred game), waterfowl and tracking wounded large game. I totally agree with the NAVHDA sentiment. Find a chapter close to you and join. Most of the chapters have training days. In these training days you will receive help and guidance from people who most likely have trained at least a few dogs; but some will be either professional trainers or people who have trained dozens if not more dogs. In the end, you won't save much money over sending the dog to a professional trainer, but you will get a lot more out of the process and your connection with your dog will be greater.

Here is a link to the chapters - http://www.navhda.us/chapterinfo.aspx

The other great thing about NAVHDA is there are tests set up to determine both the natural hunting aptitude of the dog as well as a Utility test geared more around the semi-finished to finished dog. In your case, you will probably not be able to take part in the tests as registration of the dog is needed which requires a three generation pedigree. That said, most chapters hold mock tests as their members prepare. You would likely be able to take part in these and get a bunch of value in the process. It's a great way to train your dog the right way and meet a ton of dog people in the process.

There are other ways to go, but I don't think you could go wrong getting into the NAVHDA circle.

Good luck.