I'd sell. I'd also send it registered post as you said and I'll also get insurance which is a dollar or two more just for peace of mind.
What's the card in question?
I have a standard "disclaimer" that any bidders with less than 30 positive FB will have their bids cancelled unless they email me prior because if this reason. Too risky IMO
I wouldn't proceed, if you can get out without a neg that is??
No bells going off for me. An example was my father who used eBay 1-2 times per year but spend huge dollars each time. Not everyone is an eBay whore like me