You shouldn't need to change the oil.....thats a bit extreme but you can never change your oil enough.

As i said as long as the oil level is ok start it up and let it idle up to temperatuire and i think you will find by then its stopped tapping.

And the inertia switch...........just leave it, they are a pain in the arse. Im sure they are resetable on these aswell but none the less its one less thing to play up if its removed