When we cruised on the Grand 2/4/01, we selected Personal Choice. At that time the Michaelangelo Dining Room was used for PC. There are 2 other Dining Rooms on the Grand the Bioncelli and the Da Vinci, both have an early and a late seating. Have your TA check with Princess maybe they have already assigned your seating.
The Grand is wonderful, just bring your walking shoes.
Enjoy your cruise, wish I were going.