You only need to use AS. AS will then bid on eBay on your behalf. The consensus view is that you should not place an early eBay bid as this gives away your interest and may raise the price against you.
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 .