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You can buy the replacement radiator for I think about $250 from Porsche dealers online. There are other aftermarket companies making form/fit replacements that some say have better cooling capacity. If you've taken your front bumper cover off before, it's an easy project with the messy part being having to drain some of your coolant and refill and bleed air out. Using a vacuum fill tool like the Airlift makes refilling the coolant much easier and gets the air bubbles out in one swell foop.
Once replaced add a screen. The one I have in the center installed from the front, the two sides were installed from the inside. Consider doing the two side screens while the bumper is off. I track my 2013 Boxster S and my center screen has a healthy dent from track debris. As okie suggests use a vacuum fill. There are a couple of YouTubes and "tricks" to not losing too much coolant. Getting as much air out is a must during the refill. The Jeff Richardson YouTube on Coolant drain, fill and bleeding is recommended.