Just go to the dealership and ask for the inserts that go in the lock cylinder. They have either numbers or letters on them, I don't recall which. But you can take one tumbler out at a time and look at the letter or number that's on it and insert a new one with the same number or letter. That way, once you've replace each of them, your old key will still fit and work like new. That's what I did to my Grand Caravan a couple of years ago. You'll need a bright light and good eyes or a magnifying glass to see the number or letter on the old ones. At least at my age, I did!