"Ask an expert" pattern

How much effort will a vBulletin 2.0 newbie administrator require for the following, and is there an existing example equal or close to this:

I want to operate a forum in which users can ask specified experts some questions, the answers to which are available to the forum and easy to find from the questions.

These are required:

-One click navigation from questions to answers and back.

-Nobody but the specified experts should be able to answer in a way that appears to be from the expert group.

-The experts should be able to make multiple, possibly threaded answers to a given question.

-There should be no required moderation or other administration once the forum is configured.

This is desired:

-It should be configurable whether members of the "questioners" group can comment on questions.

-With minimum administration, ability to change the forum of a question and all its answers.