I have a gazillion books, do I have to repurchase all of them if I get a Kindle?

Amazon will not give you a free Kindle download for a book you may have already purchased from them. If you have a lot of books that may be public domain books, it maybe possible to download a free copy in a format that is usable on the kindle. Check out the the Project Gutenberg Online Book Catalog.

Yes, it all depends on the publisher. Quite likely you'll not be able to get the Kindle version if you only own the actual book.

If you like to read, you'll benefit for long term though, because Kindle books are cheaper than the actual books. Amazon also gives a few thousand free ebooks for the Kindle. I've just given an answer in another question for the Kindle here, guess you may be interested:

http://answers.yahoo.com/question/index?qid=200905...

If you want them on the Kindle, and the publisher hasn't a free download, yes.