So my Cayman has 43,000 miles on it and it's 11 years old. Normally I wouldn't be worried about a water pump at this point but I keep reading the experts on the internet saying you should replace the water pump every 40k miles. I think this is *incredibly* conservative but given the cost of repairs to an M97 engine, I'm ok with erring on the side of caution. So I decided to go ahead and replace the water pump and thermostat. Once I got into the job, I thought the coolant hoses looked a little old so I replaced those, too - or at least the ones in the rear of the car that supply coolant to the big aluminum pipes that go up to the radiators in the front, and to the heater core.
I'd rate the difficulty level of replacing the Cayman's water pump and thermostat as a 3, where my Miata is an 8 and my E46 M3 was a 7. The hardest part is getting all the covers off!this stuff pictured here is essentially identical to the Porsche coolant. It's still more than good old Prestone, but half the cost of Porsche. It's made in Germany, it's pink, and it's available on Amazon. Lift Bars and they definitely make lifting the Cayman safer and simpler. The bars just plug into the factory lift points and you can jack one whole side of the car at a time. Your jackstands go under the liftbars. The lift bars are hand made to order, and well worth the cost for the added peace of mind and safety.
Finally, the hardest part of this project was filling the cooling system. I drained about 4 gallons of coolant out, so there was some still in there, but not a whole lot. I used distilled water in a 1:1 ratio with the Pentofrost E coolant. I found a write-up on how to fill the system here and it worked well. It just takes a lot of repeated burping and topping up. A week after I changed the water pump I put 1100 miles on the car and it performed flawlessly!