Here's my opinion from someone who started in the ED as a new grad...
There are many hospitals that offer a fellowship in ER nursing. At my hospital, we had several months of classroom review material (because no nursing school hits ER material) and critical care material. We then had a 4-5 month clinical practicum - work 40 hrs/week in the department with an assigned preceptor, with weekly objective reviews and meetings. It was very intense, but wonderful. I learned a lot, and because the hospital accepted new grads, the atmosphere in the department was very good (for the most part) for learning.
I don't feel new grads should jump straight into an ER that doesn't have any kind of program - the amount of things to learn is too great. BUT if I could do it again, I would probably do a year or two of ICU. I think ER is wonderful, but because it is usually a "cattle in, cattle out" philosophy, you don't always get a chance to fine tune your assessment skills.
If you are a smart person, sharp, willing to learn, and not afraid to ask questions, you'll probably do fine. You also need to be able to jump in and DO, instead of just standing outside of the door. During my fellowship, I went through TNCC, ACLS, ENPC, and the hospital paid for it
Maybe get a book (Sheehy's Manual of Emergency Care is good) and start reading. I know the last thing you want to do while finishing up school is read a textbook that doesn't contribute to school, but it can help you feel more comfortable.
Good luck. Let us know what happens.