Excellent first choice. Enjoy it!
Wow! certainly a lovely sister! If you go on Princess cruises website and then choose 'ships' you can find a review of the Grand Princess with photos too- enjoy!
Whether it is a good choice of ship for YOU or not, only you will be able to decide when you experience it for yourself. It certainly is very large and modern (110,000 tons with up to 3000 passenger onboard), so you should have plenty to do. You don't mention where you are cruising to but I presume it is the Med. cruise around Greece and Italy? Very nice! Get yourself a Pricess Cruises brochure from the Travel Agent round the corner, and in it you will find pictures of the ships public rooms and cabins together with a list of all the things that you can do onboard. Investigate the ports of call, and make your mind up what you want to see at each place! Buy a couple of travel books and have a good read. It will pay off in the long run. Happy cruising.