Bringing a pup home at 6 weeks isn't ideal, but it's not the end of the world either. GDFTB take their pups away at 6 weeks. The main problem, as you've found out, is that they don't learn bite inhibition from their littermates. Don't panic, follow the advice you've been given, join some training classes when pup is old enough and above all remember - this is normal puppy behaviour and is NOT IN ANY WAY AGGRESSION - any more than a human baby grabbing someone's hair is a sign that it will grow up to mug old ladies