Did you get through at least part one of the book? I would say that's key. If not that whole part, how about chapter 2? That will give you an excellent overview of the GTD methodology. So would the Keys to Getting Things Done webinar, which you can access through the two-week free guest pass to GTD Connect.
Then, once you've read at least chapter 2 or watched the Keys webinar, I would recommend getting either a GTD Setup Guide (if we have one for the tool you expect to use to manage projects & actions) and/or the GTD Implementation Guide. You'll find those all here: https://secure.davidco.com/store/cat...-p-1-c-263.php
Hope that helps!