Nope, spark plugs are an additional service item at additional cost, every 5 years or 54,000 miles (as is coolant and brake fluid change as well at differing times).
The only difference listed in the service schedule (pages 18 and 19 of the service booklet) between a P2 and a P3 is 15. LSD Gear Oil (except viscous coupling type) P2=Inspect, P3=Replace, and the 350 has the viscous couping type which therefore doesn't need replacing.
Everything else is identical and therefore Nissan are ripping us off charging extra for a P3 over a P2. I'd like to see someone at Nissan explain why they charge more for a P3.....