Good luck! You can get some study info at this link (from this site):
http://www.nukeworker.com/study/POSS.shtmlYour interview will almost certainly not be related to the exam sections. On the exam (I presume EEI POSS) you need to work as fast as possible (they are designed to not finish) on each section involving math.
On the interview you will be asked about previous experiences that you have had. They don't want to know if you already know how to operate their plant (though they will appreciate the fact that you have previously operated small scale systems). Most relevant will be when they (I am assuming 3 people together) ask you about things like:
1) Tell us a time when you made a mistake. How did you react when you realized it was a mistake.
2) Have you ever bought a product with some assembly required? How do you approach the project? What if the directions are missing?
3) If you are given an order to operate equipment that is damaged, how will you react?
4) What are your two greatest strengths? How do you use them?
5) What are your two greatest weaknesses? What is your action plan to correct them?
You have been involved with many boards over the years. You know they will attempt to take you out of your comfort zone to see what lies beneath.
Final advice on the interview: the interviewers should be funnier that the interviewee
Advice on the area: you will have more people within 10 miles than you had for many of your days at sea, and unlike the Navy you get to choose which ones of your neighbors you see on any given day.