Yup, gotta agree with Sheri. A good school will teach you what you need to know.
Grad school is tough, don't add to the stress with a job that you don't like and you won't enjoy. If you love doing what you are doing, keep right on doing it. You'll be surprised how much you are learning and how much will apply to your FNP program. This is coming from a person who is a L&D nurse in a FNP program, BTW
My FNP program has all kinds of nurses BTW. Home Health, Hospice, ICU, ER, L&D, Peds, NICU, Interventional Radiology, Cardiology, OR, Nursery, etc... We pretty much have someone from every nursing field their is. We even have several that no longer do direct bedside nursing and are caseworkers.