Before your post moves onto page 2, I'll reply.
I was thinking, there's no difference between a 98 & 01, but 89 & 01, lol, yip, there is.
Oil - 650ml is recommended, but a lot of people use about a quart which quietens the bike down (I just change the oil often, so use 650-700ml).
The kickstarter wears out pretty quick, but can be welded back in place (I'm having my original done at the moment, as my 1yo one is wearing out already) - not sure of exactly what is being done, but I know the guy who's doing it knows what he's doing (either that or he can find his own way to the next ride lol).
Check out the kdx pages for mods to be done - airbox for one.
http://justkdx.dirtrider.net/
Good luck & hope you enjoy the kdx - you'll no doubt find your trials skills help (with any bike) :)
Michelle