Folks, the original poster wrote "I am not knowledgeable enough to know whether I'm buying a dud or not." This rules out the usual cheap and chancy sources of used cameras such as thrift shops, pawn shops, flea markets, eBay, ... that many of the replies have suggested.

He's best off buying from one of the dealers mentioned. The all offer at least short term guarantees. But he does still need to know how to do acceptance testing on a newly arrived camera.

Cheers,

Dan