How many years are nurse anesthetists in school?

I am thinking about being a nurse ansthetist. How many years are they in school? People have told me it is a four year program, the first year being normal cles, the second bieng clinical studies, and the third and fourth being more hands on. Is this true? Will i need to do a residency before I can start working? Will I have to work for a year as a nurse first?