Whether formal music background is an advantage or disadvantage is up to you. I know a fellow who has all kinds of formal training,years of both orchestral and choral work, etc. You should hear him jam in a folk or bluegrass setting, backing up a singer, or improvising gorgeous harmonies on his viola! - Wonderful. The training certainly hasn't hurt him any. You would never expect a viola to fit so well in a folk environment.

For myself, I took four years of piano when I was a kid, then the usual "music" classes in school and a couple years playing violin in the orchestra. It didn't cure any of my bad habits, it took singing with other folkies to do that. But there are times when reading notes, doing a bit of sight reading, or knowing a bit of theory is a great help.

Once in a great while, when I can't figure out or remember a melody, I transcribe it in standard musical notation using a guitar or piano to find the notes. Lots of effort, but it works. And somehow having the mental picture of the notes helps me remember the parts I had difficulty with.