[Mammy]

Hello,
My name is Amy. I have 3 boys ages 12, 9, and 5. My oldest son is from a one night stand when I was 17 years old. The biological father knows about my son, but has never made contact with him at all. My current husband has been raising him since he was 2 and a half years old and we have thought many times of having him adopt my son, but never knew the legals of doing so. My son is now a 7th grader and has used my husbands last name for a few years even though it is not his legal name. There are other circumstances that I don't know if they will affect this issue or not, and will share them if I have too to get better advice, but I just want to know how hard it will be to legalize my son's use of his step fathers last name. My husband wants to claim him as his son legally. So can anyone help me out with some advice on how to go about doing this? Also, We live in Oregon, and the bio father was last known to live in Michigan. I don't know if he is still there or if he has moved on. Will not knowing where he is affect my quest in anyway?
Thanks for your time. Anyone, please help me with this issue.