I'm not sure what you mean by the NLN.
You may mean that you are currently taking prerequisite courses with the intention of applying to one or more nursing programs which utilize a pre-admission exam developed by the NLN as an admissions decision factor.
Nursing education is somewhat standardized, as the curricula are designed to produce generalist nurses as required for licensure by the 50 state boards of nursing.
SANE/SART training and certification vary widely, from self-study courses to certification including both didactic study and precepted clinical experiences, to post-baccalaureate and masters level degree programs in forensic nursing.
SANE/SART positions for nurses vary also - there are some hospital based programs ... others are functions of city, county and state governments. Most are not full-time, but utilize a pool of professionals on an on-call, as needed basis.
You'll have plenty of time in nursing school to get exposure to many areas. Good luck to you.