You run a risk buying from anyone. I laugh at anyone who thinks otherwise.
Ebay does well for the buyer.
I would only ever buy a locomotive* from one of two vendors I've bought from in the past who sell new stuff in the box. Rolling stock, I can fix if something is bad, but that hasn't happened either (with On30 stuff, things don't break so easy as in some other scales).
*I'm not a collector so I have all the locomotives I'll probably ever need, can't imagine ever buying another unless someone makes a On30 Army Baldwin 2-8-2 someday...