These are by far the most common misfire code culprits.
...and as they are only $8 ea , most techs just change them for easy diagnosis..
I would get two and try them before doing anything else.

http://catalog.eautopartscatalog.com/mercedesshop/sophio/quote.jsp?clientid=catalog.mercedesshop&cookieid=1M30LAGSC1OW11DN02&baseurl=http://catalog.peachparts.com/&partner=mercedesshop&year=1998&product=F1010-84561&application=000429429