How long it will take, depends on where you go and how many classes you have under your belt already.
A PA is usually a four year degree while a Nurse Practitioner is usually a 2-3 year Masters in Nursing program.
One focuses on Nursing Practice, skills the other is for Medical School wannabees. It will focus more on diseases than the patient same as a doctor does.
I'd suggest getting at least two years of floor experience in an acute care setting to solidfy your nursing skills and gain experience.
Once you have that behind you, you'll always be able to find work and you can go anywhere in Nursing or Advance Practice.
Wish you luck.
Andrew Lopez, RN
http://www.4nursing.com