I'm not sure about most of the questions you ask except the warranty one.
I contacted TopRetail4 (at least I think that's what his user name is) about several of his refurbs and asked about the Apple warranty. His reply was that they are provided as is, with no warranty whatsoever. This may be different from seller to seller, but I think that unless a warranty is specified on the auction listing, presume that there isn't one. And if in doubt, contact the seller and ask him/her to clarify it for you.
I do get the impression that these lots are ideal for technicians who also happen to sell the stuff, as they can check them out, and if they're not working, can fix them up, sell them, and offer their own warranty (eg if you had a refurb retail shop and had your own technicians, for instance).
I have become wary because of the warranty issue, and that has made me shy away from bidding on them. Maybe the other thing to consider that not all genuine Apple ipods that have been refurbished may necessarily be refurbished by Apple. If they were, then the sellers could confidently state that warranty, because ipods refurbished by Apple are given a 12 month warranty (ie see their online refurb store for details).
I may be wrong in my understanding of that - somebody please correct me if I am - but this is what I've been told.