I went from another area to the ICU and even coming in with 4+ years of experience in trauma/ED, I found it very hard to transition! The knowledge needed to feel proficient in an ICU setting is huge. It can be done and it is normal to be scared -- actually, I would expect you to be worried
As someone else posted, your preceptor is your best friend. Get all the information you can out of them. Never be afraid to ask a question. Never.
Some suggestions on reading/prepping material:
1. Your unit's policies and procedures. Read them and study them. You have to know what your particular unit/hospital expects of you before you can start doing things. Usually available from the nursing educator on the unit or the hospital.
2. Spend a little money and do the AACN critical care online courses. If the full critical care orientation modules are too much $$ for you right now, do the Critical Care Pharmacology course. It is invaluable and once you feel secure with your drug knowledge, other things will fall into place.
3. Here's a great website with informal knowledge but really helpful and FREE: index
Critical Care Nursing: A Holistic Approach by P. Morton & D. Fontaine. (used copies available for around $50-$60 on half.com or amazon
Critical Care Nursing Certification by Ahrens, Prentice, & Kleinpell. (Not just to prepare for the CCRN exam, it is a great resource).
And, lastly, I'd like to encourage you to be mindful of your progress and ask for what you need. Meet with your preceptor and manager often and if you need to extend your orientation, don't be afraid to do it.
Best of Luck!!!