CBUNA urology certification rn

I work on a urology/surgical unit as an RN for the last 3 years. I am a RN-BC. I plan to register for the urology certification exam in May. I have been told the certification test is hard. Coworkers mentioned how a lot nurses fail the exam. I bought the review book, I am waiting for it to arrive. Is the exam really that hard? Since its paper and pencil, are there fill in the blanks or only multiple choices? Is anyone a CURN? I need some guidance please.