Question: Is there a special way of communicating with Vine Reviewers? Or do you simply comment on their review like you suggested doing with regular reviewers?

You can click on the reviewers name and see if they have an email listed, email them and ask if they want to review the book.

OR  you can go to AMS.AMAZON.COM and pay $1500 to have Amazon offer your book to Vine Reviewers for you.

Question: What is the best way to find Top Amazon reviewers? How do you contact them?

I would go here http://www.amazon.com/review/hall-of-fame  and just click on each reviewer, find their website or blog and get their email address that way.  When you ask for a review, give them the option of a PDF, an eBook, or a print copy.  Make sure you include your email address.

Question: Is it best to contact them before or after your book’s release date? And if before, how far out from the release date?

You should wait until the book’s release date because they cannot post a review until it is up and you want to have books in hand to send them the MOMENT that they ask.

Question: How many reviewers of the same book would you contact? Do you find there is a point at which contacting too many seems overboard or possibly unprofessional?

No number is too high.  I counsel folks to reach out to 20-25 reviewers each week and never stop.  Ever.