Well, I just talked to my client, and I'm afraid that it will be so custom made that we can't use it as a normal e-commerce plugin. I'm not sure if it will be based on Geeklog either.
I'll keep you posted.
BTW zClassifieds can show your Ebay listings as far as I can remember.
Dutch Geeklog sites about camping/hiking:
www.kampeerzaken.nl | www.campersite.nl | www.caravans.nl | www.caravans.net