Answer
Parts plus labor. most shops have a factory service blokeual which has a estimated time for each job, which they use as their base estimate for their hourly rate. i do not happen to have the service blokeual for your car, however the normal job interval for a heater core replacement is around 2-3 hours. how much the shop decides to charge for their hourly rate is up to them. i normally charge roughly 50 dollars an hour.