Helland-Qvisling from Stavanger to Minn.

I am trying to trace my father's side of the family. I have spent long hours searching every database I can. All I had was my father's handwritten note and a probate document. The document has the date of death of my great grandfather John Henry Helland, died Oct 26, 1896 in Marshall Co., Minn.. He had a wife Guri H. and 6 children, fought in Illinois in the civil war; was mustered out in 1865; then homesteaded 1885 in Forn, Marshall County, Minn., also referred to as Crookston. He appears on a Civil War pension list. I don't know where they lived during those 20 years 1865 to 1885. I can't find any of the children on any database. I'd like to know the birthdate and surname of his wife Guri, what ship they came on from Stavanger and what year they came. It had to be before 1865 which is when he mustered out of the civil war. We have almost no data on my grandmother, Anna Quisling, who married Peter Henry Cornelius Helland, one of the sons of John Henry Helland. Her name is spelled Annie Zuisland on my father's birth certificate. I see it spelled Qvislin and Qvisland and many other ways. We know she was about 16 when they met and she may have come over by herself from Norway. Since Cornelius was born in 1880, if you guess that he might have been 20 when they married, that would be 1900. Their oldest child who lived a long life, Esther, was born Nov 14, 1908; died Jan 24, 2000. Cornelius and Anna had two other children who died, Hjalmar and Ruth, about which we know nothing. I see many Helland family trees on the web but no names on them that match John Henry Helland's children: Martha O. Nelson, b. abt. 1870; Julia Nelson, b. abt. 1876; Gustav Helland, b. about 1873; John W. Helland, b. about 1877; Peter H.C. Helland, b. 1880 (source: my father's birth certificate); and George C. Helland, b. about 1883. Two of the daughters obviously married men named Nelson. The approximate dates of birth are from the ages of the children listed on the probate document. If any of these names ring a bell I'd so appreciate hearing from you.