Run, Forest, Run!
While I don't believe that it is necessary for a manager to be the "best" or most experienced clinical nurse on a unit, it is definitely necessary for a manager to have a good foundation of patient care experience, clinical skills, and sound knowledge base in ANY area that s/he manages.
Consider your duties as a manager: 1.) Clinical, which includes providing staffing coverage as needed. How can you "fill in" on a unit which you have never worked? 2.) Administrative, which includes scheduling, hiring, firing, evaluating, and counseling staff. How can you have any "authority" in doing these tasks when your staff knows that you know nothing about their jobs? How can you anticipate the staffing or budgeting needs of a unit you have no experience working on? 3.) Education, which includes staff development. Sounds like you will be the one needing the most development. Policies and procedures are also part of staff education. How can you develop and/or revise policies with no expertise in this area of care?
Managers have 24 hour accountability for their units. Adding yet another unit to your responsibilities without significantly increasing your compensation is out of the question. Which one of your administrators would be willing to tack on 40 hours/week of patient care without any increase in salary?
It sounds to me like you are being offered this "opportunity" as a means of providing a buffer between the staff and administration. The administrators don't want to be the first in line to be called whenever a problem arises on this leaderless unit. You stand to gain NOTHING, and stand to lose much by taking this job. You will not have the undying gratitude of administration, because no one ever does. You will not have the loyalty of the staff because regardless of their feelings for you, they will not respect your authority in that unit. So even if they like you, they will not recognize you as their leader. There will probably also be 1 or 2 malcontents within the unit who will try to sabotage you to prove that you shouldn't have been given the job in the first place. (Which you shouldn't.)
Please don't misunderstand my post. I don't intend to demean your abilities whatsoever. I just don't want to see you taken advantage of, or made into a scapegoat if something negative should happen on this unit.
If they were truly seroius about providing effective leadership for this unit, they would orient you to patient care first, pay for you to obtain any necessary continuing education and certifications, and offer you a substantial pay increase. If these things don't happen, I wouldn't take the job.