The buses are not free! About 50 Kronor which is about £6 for a 10 minute ride to the side of the airlfield. Bus stop B25 Bus S44 runs every 20 minutes to the Clarion Hotel or the other hotel (can't remember the name) which are both very close to the museum (it's behind the Clarion). Opening hours of the museum are 12-4pm Thursday-Sunday at this time of year. You don't need to change any money into Norwegian, absolutely everywhere takes cards, for everything.