The best advice I can give you (besides dress in layers) is to read EVERYTHING, both before the cruise and onboard. They tell you all you need to know, but an amazing number of people don't bother to read it!
Then relax, let the staff pamper you, and play rich!
You will do great in an inside cabin, as you want to be out and about the ship and on deck most of the time anyhow. And the money you saved can go for the expensive excursions!
You can check out our 8 cruises to Alaska at
Cruising with the Halls
and some of the many possible excursions at
Alaska Excursions Guide
Have a GREAT cruise!