Iv'e never changed one on a CRM Phil so i can't say for sure, but usually you just take off the clutch cover and
remove the top cover of the pump housing and then remove the impeller ( plastic fan thing ) off the water
pump shaft, pull the shaft out ( make a note of which way the oil seals are ...

Rather than judgeing it by white gunk around the oil filler cap
check the actual color of the Oil , IE drain some out and check that
as condensation can build up inside an engine if it is used for mostly short runs and it will leave a white gunk around the filler cap.


So check the color of the oil ...

I blipped the throttle at standstill in neutral and it stuck itself at the redline even with the kill switch to kill and the key to off
is this a sign off a dodgy kill switch

I have seen this 3 times before on 2 strokes,
the kill switch and ignition were not to blame for the engine not shutting ...