Wow! Thanks very much for the uber-speedy replies, everyone. Very much appreicated

Yes, my main reason for bidding despite suspicion was that the seller accepts Paypal, but I'm still loathe to pay, because there's always a chance something could go awry and Paypal might not back me up, for whatever reason. It's just too much money to take that kind of risk.
I will do as advised and request an invoice, though I'm starting to think that won't get a reply either; at least then I'll know. I noticed, though, that only one of the auctions has an AAL option to request an invoice. The other only has options to pay/ask questions, etc. I guess I'll just get in touch with eBid admin and ask them what they think.
Anyway, thanks again for the replies. I will try and get an invoice or reply of some sort, and just wait it out a bit longer.