SC NICU RN here, so maybe some of my impressions might not fly in Maine -
First piece of advice: DON'T GIVE UP!!!!!! No one ever realizes their dreams by giving up!
I came into nursing relatively

late in life (started nursing school at 47 y.o.). Went the ADN route because of my age (and had other degrees in other fields already).
My intent all thru school was to do NICU. When I graduated, there were no NICU openings in my geographical area, so I started on the Mother/Baby unit. (figuring, if I'm gonna eventually take care of SICK babies, better learn how to take care of WELL ones first!)
A little over a year later, an opening came up in NICU and I jumped at it. Been "NICU-ing" now for a little over a year. Still learning TONS of stuff every day.
It is rewarding, exhilarating, frustrating, heartbreaking - all this and more. When you spend your shift taking care of a 14-ounce 23-week crack baby on life support, you go home with a new appreciation of what is important in life.
If I had it to do over again at YOUR age, I would probably go for the 4-yr degree, although ADN or BSN doesn't really matter when taking the NCLEX (boards for certification).
God Bless, Good Luck and I think you have a TERRIFIC attitude that will help you accomplish great things!