Quote from elkpark
The point of the exam is supposed to be to show that you know what a typical experienced RN in your specialty would know. I took the certification exam in my specialty (both as a generalist, and later, for my advanced practice certification) without any special prep courses, and did fine. There is no way I would pay hundreds of dollars for a prep course.
Unfortunately, NICU has many different types of units and the exam covers them all, not just one. For example, I work at the highest level of care (level IIIC with peds surgery and ECMO), but we don't do deliveries. Vice-versa, other delivery hospitals may not do the pediatric surgeries that we do or ECMO, or see high-risk kids long enough to get to know their syndromes very well. Another caveat is that many high level NICUs do not keep their cardiacs anymore so we dont' get to see those either...and then there is everything in between. OP, it all depends on what kind of experience you have.
I've only heard of a handful of NICUs that truly "do it all" that would allow a RN to have experience in all areas unless she or he has worked in multiple different types of NICUs.
I would also recommend NICU solutions but others have taken the one offered by ProedCenter and liked it well enough. There are two books (Core Curriculum and RNC review) that have questions that you can answer for practice.
Remember you get a 90 day window once you sign up (and it takes like a month to get eligible anyway), so I signed up before I thought I was ready so that I could buckle down and study.