Anesthesia school is much more difficult than nursing school. You delve a lot deeper into anatomy, physiology, pathophysiology, pharmacology, etc. You need a strong science background, evidenced by good grades (although with more schools popping up, entrance requirements are becoming more lax), and experience as an ICU nurse in a high acuity intensive care unit. There are minimum requirements for ICU that vary based on schools, but the bare minimum is 1 year. Personally, I think the more experience the better. For me, after one year I was just starting to become comfortable as an ICU nurse, much less proficient. For my class now, the average experience is 3-5 years. There are other programs that let you in with less, but be advised that the time requirement isn't as important as your abilities and proficiency as a critical care nurse.
You are first and foremost a nurse - although, as the previous poster wrote, an advanced practice nurse. That is why critical care experience is important, as you draw from your knowledge and experiences being involved in the care of critically ill patients. Not many people know what advanced practice nurses are - you'll often hear physicians referring to CRNAs and NPs as nurses, which doesn't take into account our additional education.
There is a lot more to it than 'just administering anesthesia," as you are often responsible for coming up with and changing anesthetic plans as the patient condition changes. It looks easy because we (CRNAs and MDAs) make it look easy. There's a lot that goes on behind the scenes.
The main thing everyone knows about CRNAs is that they make a lot more money than RNs - and for good reason. However, whatever specialty / career you pursue, do it for more than just the money. I've mentioned this many times on this site before, often with many people disagreeing with me, but there are better ways to make money than going through nursing school, working as a nurse, then going to CRNA school. Salaries aren't as great as they once were (in larger cities, at least - salaries are great in rural areas), and there's no real way in knowing if / when they'll go up. There are a large number of CRNAs projected to retire in the next few years, opening up positions and hopefully raising salaries. However, as larger anesthesia practices are buying out smaller groups, salaries / retirement benefits / vacation time is dropping. Anesthesia is a great field and career to pursue, but I'm also not disillusioned to think I'll ever get truly rich off of it.
A career that you can make as much / more than CRNAs with better hours / lifestyle? Pharmaceutical or medical device sales reps.
Oh - also regarding DNP (doctorate of nursing practice) degrees. They are expensive and are not going to help you find a higher paying job. You may or may not get more clinical hours based on the program you attend. Regardless of MSN vs DNP programs, you'll finish both as a CRNA, just with more debt if you have your doctorate. I personally don't think there is any additional clinical skill associated with a doctorate degree. Some people do it so they can call themselves Dr. Jane Doe when done with school - please don't do that - I personally think that in clinical settings, physicians (MD / DO) are doctors. Don't do a DNP program unless you have to.
There are a lot better resources than me in the SRNA
group (this is posted to the general nursing student group).