Hi, I changed my coolant at 5 years old. The manual seems to indicate that it gets changed every 5 years (by way of a footnote in the manual). My question is - on other cars, after you change the factory fill, they recommended changing more frequently (every 30k). Should I do this on the Enclave or every 5? Also I was thinking of just doing a drain and fill myself. is there a drain plug on the radiator or would I just pop a hose?