I agree with the above suggestions
In addition, I'd highly recommend joining GTD Connect if you can afford it. Read the book. Read the book again. Live with GTD for a while and tweak things as you go. The forums and webinars and other information at this site is incredibly valuable.
Then, once you've got into a bit of a groove, if you can save up for it, try telecoaching. I was unsure if the cost would be worth it but it absolutely was! The coaches here are great and having a live chat with someone even for a few hours can really focus your thinking. It was a gift to myself that I have never regretted.