I'm not a nurse but i do work in a prison. There is no way of telling whether you'll like it or not before you get there!
I would say, have confidence in yourself and your own abilities, TALK to your colleagues (nurses, doctors, drug workers, prison officers, teachers), and don't ever let prisoners "separate" you mentally from other staff. You'll hear awful stories, and probably see some awful things, and you will be seriously busy, because every department is understaffed and everyone is run off their feet. Dont ever take a prisoner's word for anything without double-checking. Be friendly, but never friends.
However, you will also find that its funny, fascinating, never EVER boring, and you will meet some of the most interesting people you have ever met in your life. I have been at my place for nearly 7 years, and i absolutely love it. I laugh, i cry, i get angry and frustrated, but i never get bored. If you want to know anything specific, feel free to PM me.