Rosenvold search

I'm researching my dad's family from Lillesands. I've found his grandfather Ole Jacob Rosenvold (age 10) and family in the 1865 census for Vestre/Moland. On other sites, I've found records indicating he emigrated and settled in Brooklyn in 1881. But I can find nothing about how he got there. I also have a copy of a "Sofartsbog" with 9th Mars 1856....is this date of birth? christening? Any guidance/assistance would be great. I'd love to find out more about Ole J's parents too. Also, I'm thinking about traveling to Norway in June. Will I be able to do any/much research in Lillesands and Grimstad? Thanks for any help!