Nice! I bet you'll have a blast.
Nothing super fancy for dressing up. There will be two "Cruise Elegant Nights" where some people choose to dress up. On Carnival, especially on an Alaskan cruise, this really doesn't mean much. I usually wear a button up shirt, no tie, and kaki pants and that's more than enough. However, there will be a few folks dressed to the nines, if that's your thing. Maybe have some pictures taken since there will be plenty of photographers.
No microwaves for passenger use. But, there is plenty of warm food to be had at most hours, including 24-hour room service (for a small fee).
Enjoy the cruise!