You need to check the FSS and see what needs to be done, it will list by number what needs to be done, such as sparkplugs, power steering fluid, etc. When it comes to sparkplugs the Dealer is going to charge around 3.5 hours plus parts...
My neighbor just purchased a 2008 E350 Sport and has Service F exceeded by 177 days! I checked it out and dealer quoted about $1G. He said, "Now i know what service F means, F*&^ this, thats what it stands for" LOL
I will be doing the work for him for under $200 using all Mercedes parts and fluids.
'03 Black Mercedes-Benz W211 165,000+ miles and counting
2015 Black X166
2014 White W166 - SOLD
2013 White W204 - SOLD
2003 Black BMW E53 3.0i 100,000+ miles - SOLD