Honestly, I would ask in the forum if anyone knows the seller. Get some feedback from people that personally know the person. As a Seller I've done this when it's a buyer I don't know and have never heard of. If the other person is seriously offended by your precautions, you may not want to do business with them anyway. I am never offended by another person asking about me in the forums.
When it's high dollar transactions, I always want to be sure!