Nice looking Seal Gray car and it looks like you have a good start on it. There's a couple things I'd like to add to the comments.
Water Pump: Water pumps in these cars often fail by age as well as mileage. I highly recommend replacing it. The best time is going to be when you plan to replace the serpentine belt and flush the coolant anyway. While you are at it, add replacing the engine mount at the same time. There are a couple bolts on the water pump that are much easier to get a (torque) wrench on while the engine mount is removed. If there is no record of the engine mount being replaced, there's a 100% chance that it is cracked. ...and while you are in there consider installing a
low temperature thermostat.
Here's a good DIY article:
https://www.pelicanparts.com/techarticles/Boxster_Tech/34-WATER-Thermostat_and_Pump/34-WATER-Thermostat_and_Pump.htm
***Notes - two of the water pump bolts are longer than the others. They go in the positions that have dowel pins on the pump. Do not put them in the wrong holes. Use the proper 'coated metal' gasket for the water pump and NO sealant. Use a Pierburg brand pump (same as original equipment). Tq 7ft/10Nm all bolts.
Note for the engine mount: I buy the insert ($) and press it in rather than buying a complete mount ($$$$). Here's the DIY:
https://www.pelicanparts.com/techarticles/Boxster_Tech/10-ENGINE-Engine_Mounts/10-ENGINE-Engine_Mounts.htm
Vent Debris: Meir did a great write up on how to take apart the HVAC system and repair the heater/defrost flaps. It was discussed in this thread:
Interior vent debris
and the instructions in .PDF form can still be downloaded here:
https://986forum.com/forums/548591-post5.html
On the 37th and 38th posts in this thread, I outline an alternative method to what Meir posted:
Interior vent debris
Welcome to the forum.
