I never attended a formal seminary school, but I did attend a school of ministry. The main difference being I didn't have a full course experience. I studied church history, the basics of theology, biblical interpretation, and apologetics. The main focus was applied ministry. It was a 2 year school but class was once a week.
My husband and I formed a ministry after we graduated which has given me some credential in the eyes of publishers. The main topic I took away after my first rejection (which was very helpful) was I needed a solid endorsement from someone with a degree. That came from a friend who does have a MDiv from Bethel University. He was someone I asked to look over my study anyway.
I don't think it would inhibit you from writing a study, but I would suggest looking into an endorser who has a degree from a well known 4 year accredited university or college. That or find a well known pastor or apologist who would endorse you.