The eBay project is designed to get you to go through all steps in the fulfilment of an actual order.  You will sell something on the eBay UK website and then complete the transaction with your buyer. 

STEP 1: Register on eBay.co.uk!

STEP 2: Decide what to sell

STEP 3: Take a picture

STEP 4: THINK before you continue

http://auctioninsights.com/

Take some time and read the section on sellers' tips.  It might help you with your planning.

STEP 5:  List your item on eBay for selling.  Provide me with your listing number.

STEP 6:  During the auction, answer any questions that potential buyers may have. 

STEP 7:  After the auction, contact your buyer regarding payment.

STEP 8:  Once payment is received, and verified, sent the item to your buyer.

STEP 9: Obtain feedback from your buyer.  Provide feedback to your buyer.

This is a very simplified plan.  You may wish to consider some intermediate steps to provide your own clarity.

Finally, the last step is to consider what you would do to deal with offering 500 simultaneous auctions.  i.e. what would you do to scale up your business from just one auction to many.