On my 2000 5.4L XLT, the "service engine soon" light came on. I took it to the dealer and they found a bad fuel injector. For $400, they replaced it and the spark plug and now they are saying that I have a blown head gasket or cracked head. They indicate that it idles rough after warming up, emits white exhaust when cold, and has exhaust gases in the coolant fill tank. I am in the process of getting a new vehicle and am wanting to sell/trade in the Expedition, so I really don't want to spend $2000 -$4000 to have it fixed just to turn around and sell it. Does anyone have any suggestions - take it to a local mechanic, etc???