Don't use 'soapy water' use a proper car / bike shampoo. Things like fairy liquid have salts in them and this will accelerate corrosion. I use Autoglym shampoo cos it has a corrosion inhibitor in it that helps. For waxing, any good car wax is fine - again I use Autoglym.
Any oil is OK for your Scottoiler, I do use pukka Scottoil cos I seem to have acquired loads over the years but used engine oil, engine oil mixed with chainsaw oil and so on have all been used by folks on here.
C&S should be OK at 17k if it has had the Scottoiler on it for all that time. Chain is meant to have some slack in it to allow for suspension movement, so be careful not to over tighten. Not sure what the chain slack is for your bike, but I'm sure someone will be along soon (or search
)