To replace a frost plug, the old plug must be removed and a new one installed in the same location. It is important to thoroughly clean the area around the hole before installing a new plug to ensure a tight fit and prevent leaks. Use a frost plug that precisely matches the hole size to avoid coolant loss. To maintain frost plugs, always use the correct amount and type of coolant (antifreeze) in the cooling system, as this helps prevent freezing and corrosion, extending the lifespan of the frost plugs.