It is risky, but you can try to mitigate that by looking at past sales and associated feedback on pinside or asking about the seller. This does not guarantee smooth sailing, but can at least reduce the risk. I'd never buy from anyone I can't find enough reassurances on, but I have bought a couple of pins from the other side of the country sight unseen and have been fine so far. You're on your own though, if it goes bad there's nothing much you can do - safest way is money on the glass as stated above