No study guides are necessary.
It's pretty basic, and mostly common sense. You obviously have a leg up on most with regard to police procedure and how your department handles calls due to your experience as a dispatcher.
Just relax and give concise, and well reasoned answers. Try not to ramble.
Make good eye contact.
Have a good closing statement prepared. The panel will usually give you a chance to say a closing statement.
Do some prep work.
Ask yourself, what are your strengths? What are your weaknesses? What have you done to address them? What have you accomplished up to this point? How has it prepared you for a career in LE?
You are bound to get some hypothetical situation questions. After hearing the question, don't just start blabbering as soon as they're finished with the question. Take a second, think about the question, then start your answer. You wouldn't believe some of the stupid things that come out of people's mouths because they feel they need to be Johnny on the spot with an answer. If you're stumped, as them to repeat the question. It will buy you some extra time. If you still don't know, trying to BS an answer to a bunch of cops is going to go over like a lead balloon. Just something to think about.
The more info you know about your department going into the interview, the better. But knowing policy by section and chapter seems way over kill to me. Just the basic down and dirty about the department and your city should be fine. (Chief, mayor, population size, area size, department size, special units, etc. etc.)
I wish you luck.