Hi, OP. These are common questions to this forum from career changers. To answer your questions…. Yes, you will need to have either an ADN and several years of clinical work experience (5 years is usually minimum for a nurse with an ADN) or a BSN and a few years of clinical work experience (2-3 is usually the minimum for a nurse with a BSN) to get a good paying job as a Nurse Case Manager. Keep in mind, although some employers will hire ADNs, most employers require a nurse to have a BSN (BAs, BSs, and BSWs are not the equivalent to nursing employers).
Also, your degree or work experience in Psychology will be helpful for your own personal knowledge, but it will not get you a job over another nurse that is new (just like you) to Nursing Case Management unless you go into a Psychology related area AND have a certification in that area that is of value to an employer. The reason being is that most hiring managers of nurses care about nursing related work experience only.
Plus, you will also find that you are not unique in having a Social Work or Psychology background and/or degree prior to Nursing. For example, I had both the BA and years of work experience in Psych and Social Services prior to becoming a nurse (I earned my ADN before earning my BSN).
Furthermore, Nurse Case Managers are not Social Workers or Clinical Psychologist. With that in mind, note that two of my current employers will not hire a Nurse with or without Nurse Case Management work experience, who has never ever worked for years as a bedside nurse. I work for two major employers in hospital settings and I am paid at the higher-end of the National Case Management pay scale, if that helps you to understand. By the way, clinicals in Nursing School does not count toward nursing work experience.
Moreover, a few employers will hire a New Graduate Nurse right out of school into Case Management. In fact, I was offered a job to become a new Case Manager as a New Grad. I was advised against taking the job by experienced Nurses in Case Management and I am glad I took the advice. Clinical work experience in nursing is VERY VALUABLE for a Nurse Case Manager because this is a nursing job! Therefore, it is not a smart thing for a New Graduate Nurse to go straight into Nursing Case Management after Nursing School even if he/she is offered a job right away.
Last but not least, you will see that your pay will reflect nursing work experience in any nursing specialty when you are hired to a new nursing position.... Thus, I also advise that you not jump around in your nursing career even though it is possible to switch specialties. Employers will pay you on the lower-end of their pay scale every time you change into a new nursing specialty unless you are working for the same company, where you can usually negotiate for the same or better pay when switching specialties. Good luck.