Last fall I started out on a 2,500 mile trip, but unfortunately had to end it about 1/3 the way through. But the first portion went very well.
I rode about 700 miles the first day with the bike completely stock. The seat was fine, but after now having a Sargent seat, I wouldn't go back. If you don't want to invest in an upgraded seat, I swear by the padded bicycle shorts. They cost about $25 but are worth every penny if you don't want to invest in a seat upgrade.
Buffering from the wind, I don't if there is a solution. Get a good aerodynamic helmet, and work on excercises that stretch your neck. Physical fitness goes a long way when combined with good gear in staying comfortable with the wind. Doing things to strengthen your lower back and abs will help posture and also ensure your comfort.
Luggage, I picked up a
Cortech Tri-Bag Tail Bag
That combined with a
Wolfman Strap Tank Bag was adaquate for a week trip. I did however not have much room for camping gear. In hindsight, I probably could have gotten a cheap duffle bag and strapped it to the seat and gotten a little more storage space. But bags I purchased seemed like they're built pretty well.
I'm planning a 5,000 mile trip for this May and the only change I'll make is to add some sport saddle bags, because I have an M4 exhaust so I don't have the pipe issue to deal with. I can't comment on how levers might impact the ride quality, but proper adjustment of them makes a big difference. Generally you want the levers rotated around the handlebars so they are inline with your arm. That does seem to help response and comfort for me.
And one other thing I'd suggest, and will get criticized for this. Look into heated gear, or heated grips at the very least. I can ride all day long on just about any bike, until I start to get a chill. Then, it's all down hill.
Good luck and safe travels.