Yea, more or less. The motor is pretty stout. The plug problem is more with the 2005+ with the 3V motor. The 03-04 have the 2V motor.
I have a shopping guide for 2nd gen Expeditions. Just search for it under my name. I think it's something like "what to look for", or look up "bubbling paint tailgate" under my name, since I talk about that in the "guide".
On the other hand, don't let the 05-06 Expeditions scare you. They do have more power, as well as more time to work out the kinks from the 03-04. Just be aware that engines with higher mileage might have issues with stuck plugs. They do make extraction kits for broken plugs, which you can usually find on ebay, or your local autoparts store.