Congratulations on your upcoming wedding and your first cruise; you have picked a great ship and a great itinerary for the occasion.
As for planning, just put yourself in Princess' very capable hands. I have seen their shipboard weddings and they are beautiful. They will take care of everything, right down to the smallest detail.
As for the cruise itself, you will find lots of good suggestions for shore excursions in the Alaska Port Chat section. If you have any specific questions about the ship or just cruising in general, we're here to help.