Hi sardineboy
If you want to retract a bid read this link COMPLETLY:
http://pages.ebay.ca/help/buy/questions/retract-bid.html
If you have won the auction then you need to contact the seller and ask them, if they will let you off the hook, keep in mind the seller is not obligated to do so.
It is vey important to read the listing 2-3 times and ask All questions BEFORE placing a bid.