I'm chuffed my post helped out Buckets.
If the filter is a foam element, you should be able to cleanse it with a squeeze of oil though it unless it's far gone. Foam filter oil is best. Chain bar oil is just as good. This should be done periodically.
As for the spark plug, I never bother changing it unless the motor stops! You can clean it up with a wire wheel as some do but I never do it.
