Train from Oslo to Bergen

If you can count on your flight being a definite, advance purchase minipris tickets are cheaper than regular tickets. Note that the Bergen line requires seat reservations.

https://www.nsb.no/en/our-tickets/minipris

Thanks! Is that the scenic route that goes along the fiords?

Bergen Line would be a direct train to Bergen from the Oslo S station. The scenic route is the so called "Norway in a Nutshell" which combines modes of transit with the Bergen Line across the Hardangervidda and the Flam Line desent to the fjords behing the scenic train route.

https://www.norwaynutshell.com/original-norway-in-a-nutshell/

The "Nutshell" route would depart Oslo about 8:30 AM and get to Bergen late evening. The Flam is a slow scenic descent followed by a wait for the boat (Aurlandsfjord and narrow Nærøyfjord) to Gudvangen followed by bus to Voss and train to Bergen. The direct Oslo S to Bergen departing at 8:25 would get to Bergen by 3 pm.

Thanks. Our flight arrives late morning so it sounds like we’ll need to go directly to the train station and book direct since the cruise departs the next day. Any hotel recommendations in Bergen?

The walking distance from the Bergen Central Train Station to the Huntigruten Ship terminal is not far, but, as you will have luggage, it becomes a taxi ride of about 6 km owing to the streets and pedestrian zone setup in Bergen.
I have stayed at the Grand Terminus Hotel - less than 50 meters from the train station. It's an old railway hotel with lots of charm and wood interiors and their breakfast buffet is quite comprehensive.
There are probably hotels near the ship terminal, but I cannot recommend one as I've never stayed in that area.
It will be chilly in March.