I may be repeating what has already been said, but here it goes -
Yes, read the journals at Crazy Guy and the various forums. Good info and fun reads.
Yes, use a route that has already been mapped, such as the Trans Am. Reduce the anxiety.
On my first tour I laid out what I was going to take, packed it, then did some training rides. This helped with ascertaining how a loaded bike would handle. I then revisited, and revisited, and revisited what I might need. I found this exercise very helpful. I still found myself sending stuff home on the fourth day of my tour.
As mentioned, buy food on the road. Determine where you can obtain supplies and plan accordingly. To minimize weight I do not take any cooking gear. What I do bring is a plastic spoon and, for emergency food, two freeze dried breakfasts (Mt. House granola and blueberries - only requires cold water to hydrate).
I have only taken a water filter when my route is devoid of guaranteed water sources and the four bottles of water I COULD carry may not be enough (I always have two full water bottles and two empty bottles that I can fill if I might need to dry camp that evening).
Ride as often as you can to get into touring shape. I have found that being in bike shape makes that first week much easier to take, then you are more able to ride into touring shape. Riding a loaded bike over long distances over a period of time is not easy, and if you find it physically demanding you start thinking about calling it a day. Don't let the mental overwhelm the physical.
Stay hydrated and stay fueled. Bonking (running out of energy) is a terrible feeling and will ruin your day. I carry half a dozen energy bars with me each day and I make sure to not go long without ingesting food, or water.
Embrace the challenge and you will find the ride will be worth it.
Best of luck.