Starting to research our trip for next May. Plan to fly into Oslo then train to Flam and ferry Bergen and train back to Oslo, spending about 2 days each city. It seems a rail pass is the best option price wise ( is this correct?) My main question is train from Oslo to Flam, we definitely want to do the historic Flam rail , so would I get a reservation to Myrdal and then a separate one to Flam or just one for whole trip - I am assuming I need to change trains in Myrdal? Also has anyone done the ferry from Flam to Bergen?
Yes, you do have two separate train reservations en route to Flam, with the connection at Myrdal. The price of a Eurail Norway pass is the same as full-priced tickets for Oslo-Myrdal and Bergen-Oslo, and then gets you a small discount on Myrdal-Flam. It's not particularly a savings, unless you have a way to use the third train travel day. Some advance purchase ticket discounts are also available, but the Norwegian web site has not always worked with US credit cards. Both your credit card and their web site may work differently next year. See also https://www.ricksteves.com/travel-tips/transportation/trains/norway-rail-passes#passes.
This week I purchased a ticket from Oslo to Flam from NSB ( Norwegian train web site). It is one ticket with a change of trains in Myrdal. My credit card would not work, so I opened a Pay Pal account and used that to purchase my ticket. The senior price was pretty good!
I discovered through Lonely Planet minipris tickets. They are reduced prices that come out several weeks before date, so probably won't need a rail pass. Thanks for all the good advice