So many questions.I serviced my Gs300 sport just before i left Toyota/Lexus.I replaced the diff oil,a.t.f(you have to get the right stuff,think its dextron 5),brake fluid,spark plugs(use the ones that are ment for the car,sport is different),coolant,re-gassed air con and changed pollin fillter.i allso added prolong engine and gearbox oils,not sure how much it works but lexus and toyota both recommend it.I have a k&n air filter so did not change that.The engine oil was castrol magnetex,diff oil is castrol syntrax.If you are keping the car then change the lot,you know it has been done then.The gear box was much smoother after the oil change,it felt great before!.I change my pollin filler every year,it makes a big differnce.Known problems are noisy brakes from pins and slidders,if you are doing them then that sorts that issue out.Check all front ball joints out for wear,and thats really about it. :winky: