You have some great goals.
I would suggest finding a bookstore and purchasing:
1) The south beach diet
2) Food for fitness
The first will tell you what foods to avoid for your normal eating, but keep in mind that some of the things that you should avoid during normal days are exactly the things you need when you're riding. The second will explain a lot of that, so if you can only buy one, buy the second one.
I would look for a local bike club and see what annual rides they do, and see if you can hook up with some group rides.
I'm 6'2" and 172, and I'm about as light as I want to be. Well, that's not true - I'd like to be lighter so I can keep up with the wispy climbers I ride with, but I'm realistic, and probably don't want to be lighter than around 165.
As far as food, the general rule is that the more it is processed, the worse it is for you.