Hi. Here are some things that will help you out.
JUST IN CASE!! Check out my page on the VIN for your bike.
KDXGarage - VIN Information
I am not doubting that it is what you say it is. I have read too many stories of someone buying a bike thinking it was one year model, then after they spend money on parts, find out it is another year model.
A 1999 KX250 is also referred to as the KX250-L1. The 1999 - 2002 KX250 models are in the "L" series. All four models are somewhat similar. Some parts fit all four years. Some parts only came on one year model. Heck, some parts may fit MANY year models.
Look on Welcome to Kawasaki.com
under Owner Info, then Parts Diagrams to find a menu which you can use to select your bike and view the parts diagrams. There is a print feature shown for each section, but I have not tried it to see if it works.
When new, your bike came with an owner's manual. It is about 5" tall and 8" wide. This is about $15 from Kawasaki. It lists some very basic service related information. There is also a service manual from Kawasaki. It is Kawasaki part number 99924-1244-04. I bought mine from Rocky Mountain for $30, but I know Ron Ayers Motorsports - Motorcycle, ATV, Jet Ski and Generators Parts and Accessories
has them for $32.50, plus shipping.
There is a Clymer manual for the 1992 - 2000 KX250. It is for service. I think they are close to $30. If you are only going to buy one, I suggest that you buy the Kawasaki OEM manual.
That should keep you busy for now.