GirloftheSun: I think 2 day review classes can help to a certain extent. If you are willing to pay the fee then go right ahead. I hope you can get a refund from where you work as part of you education benefit. Stick to the ONS test blueprint (that comes with your application form and available online at the ONS website). I don't think it's a disadvantage that you are working in transplant. I think it's a added benefit. Keep on learning, be curious and keep on asking questions at work. If you have a Clinical Nurse Specialist they are good resources and also the oncologists that you see on the floor. I usually pop a question to them and they are more than willing to answer.

Good luck again and do let us know about the results!
Peace.