While a modern pair of USD forks would be nice, not sure if you really want to spend that kind of money on the KDX. While still a great bike, there are other chassis limitations that you just can't ignore compared to other bikes.
At the very least get the forks tuned to your weight and riding terrain/style. The shock as stock is pretty close given your weight. I sent my forks out to MX-Tech for stiffer springs and a re-valve and have been happy with the results. Get some better tires too. Michilin S-12s are great here in Michigan.
Try different clicker settings on the shock to dial it in better. I've found that I needed to go quite a bit harsher (screw in) on the rebound (bottom adjustment) for the bike to handle better in the whoops. FWIW, I'm 5'9" and 185lbs.
I recently put on a steering damper (WER). I only have about 85 miles experience with it, and am still getting used to it. The front end definitely feels "tighter", more solid, and tracks better. Initially though I wish the damping adjustment was within reach while riding. I probably had it on too tight a setting. Although it was good for 3/4/5 gear sand/whoops, suddenly I was in 1/2/3 really tight switch backs, and could feel that it was more effort to flick the handlebars back and forth. A little disconcerning when trying to fly through the tight stuff! At the next stop I reduced the damping a little, but would have really of like to been able to do it whenever necessary without stopping.
Do some searching here on this site. You will learn a year's worth of experience in only a few days!