This brings to light one of the things that often make's communicating what a car needs to a customer difficult for shops/techs. You have listed four questions about the car, and then one that is completely unanswerable in the querry of how much will it cost. First without properlly diagnosing the issues, the cost to repair each one is a complete mystery. At least I can save you one though. The dome light, getting dim when you start the car and then getting bright once it started, is not in itself a way to describe a symptom of a potential issue. At the least, what you described is normal. But if there is something going on with the way the car starts, and you looked at that to try and get a clue, tell us what the car doing. That way you can practice telling the shop/tech and he/she/they will have a better idea of what the symptom you are reporting is and how to reproduce it, and then diagnose it.

The check engine light simply means the fuel injection computer is detecting something out of range. The fact that the light goes back out means that it's not always out of range, but far enough to be a concern. That would be diagnosed all by itself, totally unrelated to the other issues you raised.

The theft light blinking could be related to the door ajar switch not working correctly, and it also could not be. I'd say deal with the door ajar switch, and then see if the theft lamp stays off. If not it will have to be diagnosed seperately.

Try spraying a liberal amount of lubricant directly into the door latches on your Taurus. The switch is in the door at the latch, and over time it gets gummed up and sticks. Lubricating it should return it to normal operation. Cheap and quick! I found this tip on a Google search when the dome light in my 99 Taurus LX refused to turn off, and it worked. I didn't have the passive anti-theft, but it makes sense that it could be caused by the same thing.

It isn't odd that all these lights are going on at the same time? Theft light flashes at different speeds, door ajar is and on and off thing. Nothing is going on with the car when I start it. It is running and starting great. It is just these lights. A fuse or something?
I have never, in any car, noticed the dome light getting dim and them considerably brighter, then normal when starting the car.

Try the lube, trust me. My Taurus did exactly the same thing with the dome light/door ajar indicator going on and off. Eventually, they just stayed on all the time, so I pulled the bulb (Door ajar indicator still came on, but at least the dome light didn't drain my battery). After I did a Google search I found a couple forums that discussed this very issue, and the fix was as simple as spraying lubricant into the door latch. I used WD-40, which is not what they recommended, but it worked. You have nothing to lose and it might just solve that problem.

Do you get the "driver's door open with key in ignition" bong-bong-bong? As you didn't comment on it, I would guess not. If not, then it will be one of the other doors. I had a 95 Windstar that must have been the first year of Ford's attempt to improve on the door switch, because when it happened to my driver's door, the dealer didn't even know where the switch was! Try driving through a questionable neighborhood at night with all the interior lights on and the "bong-bong-bong" distracting you! Not a lot of funÂgee, thank you Ford!!!

Be thankful that Ford uses a better switch design than the Saabs of the 60s, these must have cost all of $0.23 per vehicle and had close to a 50% failure rate within 3 years !
But now they are nigh perfect.
Both companies need better dealer service....don't they all ??