Non-Mazda mechanics have told me my rough-running check-engine-light flashing Milennia needs $3-4K of work, including a tune up, coils, belts and more. Could it possibly be that a lesser repair will solve my woes?
Most Mazdas ar very reliable and reasonably inexpensive to fix. The Millenia was an attempt at a luxury car and does not fit any of the above descriptions. A friend of mine wanted to buy one recently and I strongly advised against it. This car can become a real money pit. I would dipsose of it.
Part of the problem may be that these non-Mazda mechanics may never have worked on a car with the unique Miller Cycle engine, like the one in the Milennia. Your non-Mazda mechanics may be correct, or they may be very much wrong. This is one case where the Mazda dealership will have much more experience in diagnosing a problem with that odd-ball engine.
However, if it has been quite some time since your spark plugs, filters, and fluids have been changed, you can at least start with the required maintenance and see if it improves the situation. Maintenance does not amount to $3k to $4k, so apparently your non-Mazda mechanics are talking about repairs in addition to maintenance. Begin with maintenance, and then see how the car runs. If it still runs badly, try the Mazda dealer.
That CEL (check engine light) is just a kid in class waving her hand trying to get you attention because she has the answer. You need to have the codes read. Some places will read them for FREE. Try Autozone or Advanced Auto Parts. Get the exact code (like P0123) not just their translation into English and post it back here.
That may help us make a little more intelligent guesses. OK it may help those who know a lot more about it than me, make more intelligent guesses.