The only way I know is to relist directly through eBay. You can change your description, title, shipping options, category, almost everything this way. You will need the eBay item# of the original listing...just type that number into the main search field and your original listing will come up and then click "Revise".
When you block a person, they can no longer invite you to a private message or post to your profile wall. Replies and comments they make will be collapsed/hidden by default. Finally, you'll never receive email notifications about content they create or likes they designate for your content.
Note: if you proceed, you will no longer be following .