You should do it. You probably have much to offer. People change careers all the time. Having a credential like an RN designates you as one with special skills and opens up more job opportunities. I personally came from higher education where landing a job is based on professional network, experience, and seniority. 100s of applicants with PhDs vying for one spot that doesn't pay well and having to impress people who (sometimes) think a bit too highly of themselves.
About the long grueling hours... That is just a fact of life. You'll do it whether you're working for tips or for a salary. I'm in my final semester, but so far I like the fact that job prospects anywhere I want to go are already brighter. Furthermore, there is this tough, real, and raw human experience element to it which I thrive on and that I never found in the higher education/office work world. It was the third best choice in my life. Number 1 being Christ, 2 my wife, and 3 nursing. Do it, YOLO!