Simple, cheap, effective auction site required like many of the eBay clones available at present for use on a Linux server with MySQL
Categories and Sub-Categories, Searchable
MUST have its own paying system simliar to ebay with paypal. (Paying for the good only after you've recieved it)
Classifieds and AutoBid function for buyers would be nice.
There will likely be extensive follow-up work for winning bidder once site is "off the ground".
Should have email system so the system will send emails out when they are outbid/ auction closing or any other stuff.
Sellers should be able to show their status for msn/skype on their auction page.
Something you've already written is fine.. there are many posted here and at other freelancing sites.