How much does it cost to replace the spring in oil pump motor?

What is your question?

This my wife's van. Check engine light stayed on today. I took it to the dealership per owner's manual. Mechanic is telling us that oil pump spring is stuck causing oil pressure changes and check engine/ malfunction light to come on. Van has 59,500 miles and regular maintenance with no prior problems. Dealership recommends replacing oil pump spring and will take 5 hours as it is time consuming work. Do you agree with their assessment?