Fork oil change

[Simon.Pieman]

seriously now!!!
to do a proper job you need to fit new seals and clean out the crud that has gathered in your fork legs.
allow 6 hours to do it properly (if you have access to an airline).
get some wd in a non aerosol form, pour it into each fork leg, bleed the damping up to work it into all those little orifices, pump it a bit more and drain. dry with the airline through the damper rod bolt hole (bottom of fork leg).
no special tools req'd apart from rattle gun or damper rod holder, jut a methodical manner and somewhere clean to lay it all out.

To do it 'properly' would actually mean dismantling the forks and cleaning the valve stack thoroughly and checking wear on the bushes, rather than messing about with WD40 (which incidently has no detergent properties so wouldn't do much anyway)
In the interim of a strip down, draining the oil and replacing with new is sufficient.
No need to replace seals if they are not leaking, K-tech don't, there's no reason to.