Well...the deciphering is kind'a tough, actually......
R/R the piston is good insurance. I congratulate you on THAT choice vs: using the money for something 'shiny'.
You didn't mention rings for that piston..but I'm sure that's on the list.
Other than verifying the KIPS is indeed working properly, I wouldn't be taking apart a few months old powervalve. Other opinion likely varies.
Suspension improvement is a wise choice, too. Respringing the frontend of the KDX is a
very good choice on the list of 'mods'. Do NOT,
NOT use the stock spring spacers. Honda XR springs will be in the neighborhood of 530mm in length, the oem springs are 470mm or so. You will need to fashion your own spacers out of 1" PVC. Schedule40 preferably.
Gear? Get everything you can afford!! You don't mention a chest protector. Twice just this year I've been in situations where one of them very likely saved a life. No kidding!
Maybe you feel like a goon all dressed up in battle gear...but it's cool when a 5yr old kid wants to talk to you 'cuz he thinks you're a
PowerRanger.
..and it will save your bacon sooner or later!
When you are setup with gear and suspension..consider some carb work. The 220 comes with a 33mm carb, and that throttles (as in gags) the engine a good bit. Either a KDX200 carb (35mm) or having RBD modify your carb will be a
BIG 'go-fast' mod.
Have fun!!