$400 sounds very close to right to me. I would expect you to pay a minimum of $300. Make sure the check the water pump at the same time as it is a lot cheaper to replace it now when you change the timing belt as it runs off the timing belt. If you want to double check the cost, I would go to Car Talk’s Mechanics Files site at
Enter your zip code and you will get a list of mechanics in your area that other consumers have used and highly recommend. Look for ones that specialize either in the make of your car or the type of problem you have. Call 2-3 of them and ask if they can give you a ball park figure. I have personally used this site with great success to find good honest mechanics and can highly recommend it. Good luck!