Technically, the bureaus are supposed to investigate within 30 days. I think the issue is often that they aren't exactly thorough about it. If it's denied or you don't get a response, you may have to appeal to the Consumer Financial Protection Board at consumerfinance.gov.
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 .