
Sometimes a pup from a 'pet' litter can turn out really well due to really good breeding further back, for example if the grandparents were show dogs/champions.
I fail to see how the breeder could say they had show potential if they have never shown, and have nothing to go on.
Why not Google the grandparents names an see if show results come up for them, if so then there is a pretty good chance that the pup may have inherited the right characteristics.
The only way to know is to start training at ringcraft enter some shows under judges that know the breed (you need a few opinions), and see how you do.
If after this you find that your dog is outclassed nearly every time, then no harm done, you Will have learnt a lot a nd further down the lien you can get a companion from him from an established breeder of good show quality stock with a track record of selling show pups to others.