A month ago I got a 2000 black/ black coupe with 87K miles. Yippie!!!
On day 1, I washed the car, on day 2 I did the clay bar and ceramic clean up, and on day 3 I reminded myself to stop staring at it so my wife would not get jealous. On week 3, my German car guy did a Post Buyers Inspection. He scanned it with AutoLogic and says "the cam deviation measured fine." He says the only need is to change "the ignition lock housing."
For next month, "What are the top 10 DIY things I need to do in the 1st 3 months?" A non-Porsche mechanic neighbor will help me.

Change all fluids, unless you have evidence the fluids don’t need to be changed.

If you don't know the service history, Porsche will recommend oil and oil filter, brake fluid replace, air filter, spark plugs, differential fluid replace and transmission fluid replace.

Beyond that,. Wiper blades, headlight restoration. Other detailing stuff.

Check and grease any rubber lube sunroof rails and check all debris are cleared from drain holes and there are at least 6
2 under the battery 2 next to sunroof and 2 rear by the back window

there are 7 I think. 4 in the sunroof at each corner, and 3 under the bonnet.

Thanks… We will jump on the fluids and filters this weekend. One question, when the car is sitting still and idling, I hear a rattle. When I press the clutch, the rattler stops. Any suggestions?