I've been to Alaska a couple of times, but not on Princess. I've sailed Princess, but not to Alaska! In any case, you're going to love cruising and love Alaska.
There are several things to know during and after the booking. As someone new to cruising, are you using a travel agent to help? You want to watch for things like which deck is best for you, the type and location of your cabin, whether you're getting the best pricing, the differences in dinner times, what and how much to pack, cancellation insurance, and several other things.
As for the pre-boarding, make sure you have a current passport, and make sure you input all your information into Princess' computer via their Cruise Personalizer at least a couple of weeks before you sail.
And of course, report back when you return and let us know how you enjoyed it!