If you're in LA, you may want to see what these folks have:
Porsche dismantlers
3. IMHO I've never seen a Porsche with "awesome rims"; the 987 base rims are pretty average looking (actually I think the S rims are worse). BMW? they have some crazy-nice rims (once again IMHO).
4. I assume you have the 16s now, so if you want to go OEM N-Spec you'll need:
205/55R-16 (front) 225/50R-16 (rear)
Bridgestone Potenza S-O2
Continental ContisportContact
Michelin Pilot SX MXX3
Pirelli PZero System Asimmetrico
(you'll need one of each...just kidding)
N-Spec tires aren't cheap and Boxsters are hard on tires...but I would 1) make sure you're going to keep the 16s before you buy tires (obviously) and 2) don't shortchange the tire selection in favor of spending that money on rims (IMHO).
Tire info
6. Some 76 stations have 100 instead of diesel. The sign on top of the hose is white instead of green, one station being off the 5 at La Paz in Orange County.
Unless you're tracking your car (and even then) I suspect you'll just be wasting your money.