New parts..chain, triple clamp, bar, guards

If you put Barkbusters on the stock bars they will make them a whole lot stronger right off the bat. If the stock bars are comfortable to you use them until you mangle them then buy new bars and transfer the 'busters to your new bars. For sure an O-ring or X-ring chain. I'm thinking about checking into those stainless steel sprockets when it comes time. Maryland has lots of rocks, you may want to consider a skidplate. As for a pipe there's a ton of posts about the different brands, do a search and see what comes up. I'll be in the same boat , as I'm going to put a new pipe on in the spring.

I don't think they meant triple clamp, more like top clamp, a one piece clamp that does not allow your rubber mounted bars to tweak so easily.
All 1 and 7/8 inch bars work for kdx's, it is the bend of the bar that is different. Most guys seem to run CR high bars. Since you are just starting out I would run a standard Renthal instead of the FAT bar, less money you know.
Bark busters, buy the kind that are metal, like fredette sells or if you don't like the biggness of the plastic they have, Acerbis makes a rally guard that is smaller. These bolt right up to a standard bar but require another kit for FAT bars, I think. Metal bark busters also improve the strength of your bar so it does not bend as easily. Also it protects the levers.
96 KX levers fit the kdx and are shorter than the long kdxers.
I kept breaking my clutch perches, so I bought an aftermarket, forged perch. You can spend little or loads of money, go with the bare minimum for now and carry the stock as spare. You won't find the kdx one, but the kx one you will.
When you buy an aftermarket pipe it should be protected with a guard such as an Eline carbon fiber one. I had a new pipe and crunched it the first day out, ruined it. HINDSIGHT.
Don't get to wrapped around the axle with doing too much modification to your bike. Ride it, maintain the filter properly, grease the swingarm bearings, which may already be in need of grease, and oh have fun.

Hey, take it from me, I bought a new 03 200 in July...
1) Buy a service manual ASAP. Just do it, you'll be glad you did.
2) Go to the "JustKDX" web page, click on Tech Tips, and print out the "New Bike Prep" info. Believe me, everything in there is dead-on correct, so instead of buying all of those hop-up parts right away, invest in a service manual, lots of spark plugs (you'll see why in the next item) and a container of Bel-Ray waterproof grease...you're gonna need it!
3) In all likelihood, you WILL need to re-jet your bike. If you haven't done it before, relax, it is easier than you think. While on the JustKDX "Tech Tips" page, print out the "Carb Tuning" info to get you started. When you convince yourself that you need to lean out your jetting, go to www.sudco.com and order several main and pilot jets; they are cheaper there than at your local dealer. The 03 200 comes stock with a 160 main and 48 pilot...I'm down to a 152 main and 40 pilot and I'm still not done. And don't ask anyone on this site what the "right" jetting is because you will just open up a can of worms...proper jetting is a function of your riding style, location, altitude, relative humidity, temperature, etc etc etc.
4) The barkbusters are a good idea. If you put them in your stock bars be advised that "vibration reducers" are inserted into your bar ends and you will need to drill those out, otherwise the barkbusters won't fit properly. (I learned that right before I had to buy my first set of replacement handlebars.)
5) Radiator braces are a good initial investment too; Works Connection works well and isn't that expensive.

Hope that's enuf for ya! Let me know how it turns out!