Hi: I bought my 300C HEMi about 1 1/2 years ago with 34000 miles. It was a Pre-Certified Car.. It appears to be a secret at what milages a Tune Up is Necessary.. Any help will be appreciated

:kap:Yesterday I left my 2006 300C AWD at the dealer for it's 30k checkup which is around $340 and includes tire rotation, alignment, oil/filter change. etc. I then received a call that it needed new spark plugs and tune-up because the original plugs are copper and not platinum for about $340...