I installed 1996 KX125 front end to my 1999 KDX without much trouble at all. Having the whole thing like you have really helps. You will need to press out both stems and put the KDX stem in the lower KX triple clamp. The bearings will be reused if in good shape. A spacer will be needed on top of the nut that bolts the stem to the frame due to the length. You will see when you fit it all together. To shim up the difference in the smaller KDX stem to the larger hole in the KX upper triple clamp, stop off at a hardware or hobby store and get some shim stock. Basicly, that's all there is to it. If the KDX stem isn't a tight fit to the KX lower triple clamp, have the machine shop you are using to press the stems knurl the KX clamp. This reshapes the material and doesn't cut it. The knurled fingers then provide plenty of grip to to stem. My 1996 forks needed rebuilding and I recommend a spring weight of .42 if you are over 180 lbs and like to ride fairly agressively. I had Race Tech install gold valves, springs and fork seals. Good luck and if you have questions, I'm here to help.