Also, real volks have the actual Japanese manufacturers sticker on the back part of the inside of the wheel. But since he powder costed them, I'm sure its safe to assume they were taken off.
You could always get the seller to take a picture close up of the stamped volk racing logo on the wheels.
As for the stickers, they will probably not be the best of quality if he gets them for 15 bucks. I bought these replacement stickers from here
VOLK RACING decals for TE37 Wheels: Blue and they were 28 bucks shipped.
Also here is another place that sells stickers
Acromann Online Shop
I believe these are real, but it never hurts to ask for more pics.