When do you change the plugs, wires . Core packs mileage??

What is your question?

I Own a 2011 a6 3.0T Quattro at 98,200. Have had some the the small problems listed but haven't seen this one. The steering movement from top to bottom has stopped. Forward and back work fine. Anyone? Also want to do preventive maintenance, I know the saying,if it's not broke....the big ones I know, timing chain,tensioner, not trying to miss anything while its opened up. Thank you in advance.