Neither have I...=/ The farthest I've ever been is Arizona...00 You really walking? That's...AWESOME! Take SO MANY PICTURES! And put them on here when you get back. Yes, very oh dear. I really hope you have fun.
Congrats!!! Okay first off you need the right shoes. Get running shoes, go to a store that actually knows what they are talking about... small little running stores are usually the best. Second, make sure to bring your camera... you might not be bringing your lap-top but you MUST shoot while you're walking... and it will be a good excuse to take a breather from time to time. And third, write, write write. I travelled through Europe and next to all my photos my journal is my most prized "memory" of that period of your life. Dont go expecting anything, just go and let the journey teach you as you go.
Oh, and start walking NOW! Use your arms... they control your legs more than you would ever think.