I bought my Nikonos V and a couple of strobes off eBay - no problems whatsoever. Just don't bid on stuff from someone with no feedback, or any negative feedback, or on an item that just has a description and no photographs of the actual goods you are buying.
If you do buy stuff off eBay, you're not really protected against the camera turning up not as described (unless there are fraud laws against this sort of thing, but I don't know the US laws are being an imported diver - maybe some states give you protection), but the safest payment method in a private transaction is a USPS money order. If you get ripped off, report it to the post office and it becomes a case of mail fraud, as the person who scammed you has accepted a post office money order as payment. You get a refund from the post office, and they get charged with mail fraud, which is a federal crime. DON'T use one of the online payment services like PayPal, as they can only re-withdraw the money from the seller's account, and if the seller is defrauding you, they will empty that account of any money as soon as it is cleared, and the payment service will just turn around and tell you that there is no money in the seller's account to refund to you. Different online payment services might have different policies, but I've heard of people being scammed in this manner.
Hope this helps! Also, if you buy used gear, don't forget to factor in the cost of a service which you should get done before using the camera (although I think you can do a Nik III yourself?).
Also try
www.backscatter.com in Monterey, they sell second-hand Nikonos gear.
Kind of assuming you're living in the US for this advice... but now I see you're in Yap...
