My question involves name change laws in the State of: Montana

I was 17 when I had my daughter and I have no idea who the dad is. I was the first to pass out a party and I woke up pregnant. So my question is I gave my daughter my maiden name, Im now married and my husband is the only daddy shes ever had so what do I need to do to get her last name changed to the family's? Ive heard step parent adoption is way expensive, if its cheaper to get a name change we can do that, just need help with understanding the process. Thank you.