hello. currently I'm in a crna program and I can see you're interested in becoming an ICU nurse and also a crna? (I saw one of your posts said, crna? sorry if I misunderstood? LOL)
answering your question - you can sit for the ccrn exam after about 1500 hours. meaning about 9 months into your first year as a full-time nurse, this DOES include orientation hours (if you're the main nurse).
as for your second question...how to get that ICU job:
I would really recommend starting on a medsurg, tele, or pcu first. I was about 23 when I became a ICU nurse and got accepted quite easily. I had about 1 year tele experience under my belt. I worked hard on my tele floor, received drips, chronic vents, ekgs. I even got my critical care course - which is a ICU led course which teaches you all about ICU type of patients.
it was quite smooth transitioning into ICU. while you're hired at a hospital, all certifications such as acls/bls/pals will be paid for. so I wouldn't worry about it too much.
if you're not wiling to go to tele first, (Which I totally get. I was impatient when I was younger) id recommend being a pca, or like you mentioned getting some sort of externship. id also recommend as you said getting a acls certification, iv course, ekg course, just to prove that youre a go-getter.
I was actually able to grab an ICU position straight out of nursing school at 21, but I had to resign because of personal issues - and decided that going the tele route was more suitable for me. but like I mentioned, I got an acls cert., iv course cert., and ekg course. I had a good GPA, good recommendations from my teachers, and I had also volunteered as a hospice center prior. so it was smooth getting that ICU positon.
anyways as for the crna portion question? (again, sorry if I misunderstood the question)
currently 25, and I got into a crna program. I worked 2.5 years, passed 100/125 score on the ccrn, became employee of the month, got good recommendations, received open heart patients (the sickest type of patient), shadowed crna for about 40 hrs --- then started applying
got into my dream school
hoped I helped. any issues, let me know