Yes, they will either time out (if the maintenance lasts longer than your re-try time) or they will go up after it is over, if your re-try time is set long enough.
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 .