I had the dealer do my spark plugs. No issues and about $150. The new Motorcraft plugs are one piece and have longer threads. The Expedition is on a, top 10 list, of vehicles that go high mileage(200+). Do you have a mechanic, to take care of say, ball joints, brakes, tierods, coil packs, fuel filter, serpentine belt/tensioner, and other routine maintenance? The fluids, will all need attention. A/C repairs are big bucks. A good set of tires is $700-800. I purchased mine, 8 years ago around 76K and it has been nickel and diming me. The money I spent, I probably could be driving something newer, if I traded up. I have noticed Fords (and other brands to be fair) hit 80K, everything starts going.