Beginning January 24, 2001, all Porsche vehicles are now factory filled with 0w/40 Mobile 1 synthetic engine oil. It's readily available at most of the part stores.
Based on your driving style, I'd replace the oil at every 5000 miles if you do a lot's of short distance, stop and go driving, 7500 miles with more long distance, highway miles.
Beside a good quality oil a good quality filter is also important. Use the OE Porsche or Mann filter.
I'd suggest to find a good Porsche specialty shop, they should have everything necessary to service your SUV in the right way.