Reading too much will be likely to make you think you need a lot of stuff that is definitely not necessary.
For me, it was just the opposite. The more I read, the more I saw how much trouble people had early in their tours with overloaded bikes and how much stuff they mailed home. So all that reading convinced me of several things: (1) Don't send stuff home--leave it home in the first place, (2) Take stuff you will actually need, not stuff you think you might need, (3) Do at least some riding close to home with exactly the same gear you will be touring with.
Everybody is different with how much preparation they want to do. For some, intensive preparation reduces stress and allows them to enjoy the trip more. For others, intensive preparation takes all the spontaneity and fun out of it. Figure out what camp you're in and act accordingly.
I read a lot of journals over at crazyguyonabike.com, and a lot of forums both here and at CGOAB. This added many problem-solving options to my arsenal. I saw what problems others had had and how they had solved them. That gave me a lot of good ideas, which not only helped me feel comfortable that I could cope out there on the road, but it helped me solve the day-to-day issues I actually did encounter. Furthermore, it alerted me as to what I might want to stop and see along the way. It's a bummer when you later realize that you passed close to something really cool but didn't stop because you didn't know it was there.
Oh, and if you want to make sure the trip actually happens, set a specific starting date now, tell everybody you know, mark it on your calendar, and start counting down the days. I counted the days down to my first major tour starting at 815 days out.