Whilst there are some good Ford dealers (both from a sales and service perspective), far too many of them come across as mouth breathing droolers.
As a rough guide, definitely change the oil and oil filter, along with the fuel filter and air filter element. Then have the EGR system checked (and cleaned if necessary). It can cause fuel economy and performance to suffer. This is what I'm referring to:
And a small article about EGR blockages:
http://www.hypermiler.co.uk/egr-valv...-valve-egr-faq
PS. Diesels don't have spark plugs.