Hi, i just bought this book - the ROR Lenz book.

I have a macbook with leopard 10.5.1 - so my ruby and rails is updated past the book versions... ok, but I'm trying to download the mysql and for the life of me, i can't find the standard dmg file... i have found a community download 5.0.45 but its a tar.gz ?????? what do i do with this, and is this the right path?

Help - I'd like to get started with learning