I would just contact Cliff...he is honest and knowledgeable. If a dog is trained right, it is not a liability.
One reason I'd rather go with a pup, so I know exactly what training has been done and IMO the journey is worth it. It shouldn't be rushed though, a 3 yr old adult dog is barely 'finished' with the training that goes into PP or IPO.
A mature GSD with good genetics that you train(with the help of a club) will protect you just like any 80 grand PP one would.