You should change the plugs because if you leave the existing ones in there,
you run the risk of the plugs seizing themselves into the holes and when you
attempt to remove them you can damage the soft aluminum cut threads.
when you put new plugs in (use NGK's), make sure you put a dab of anti-seize
on the threads to prevent the problem for the next tune up.

Also change gas filter and air filter and check the cabin air filter.