The Nilsens

Hi! I'm hoping you lovely people can help my husband and I! [:)] We are researching his family tree and have found it traces back to Norway. This is the information we have so far: Christian Severin Nilsen was a sea-man born around 1849. We think he married his wife Walborg in Norway before coming over to the UK (Liverpool). Our first record of them in the UK is the birth certificate of their first child Ruldolph Nilsen in 1879. On this record Walborg is listed as 'Walborg Elizabeth Nilsen formerly Rekvoldsen'. Obviously it would be great if we could delve deeper into the family history, but we have no idea of how/where to start with the Norwegian records![:I] Any help you give would be VERY gratefully received! [:D] Many thanks in advance!