The best training is a masters or dnp (doctor of nursing practice) of science with a specialization in nurse anesthesia. CRNA programs range in length from 2-3 years and can cost from $15,000-$120,000.
Though they have been ranked by U.S. News and World Report, the rankings are very subjective. The best training program is one that fits into your life and your budget.
If you're looking for a CRNA program that fits your needs, I recommend www.all-crna-schools.com. It gives a complete listing of all the schools with details about each one.
Ongoing certifications include PALS, ACLS, and BLS. CRNA re-certification is required every two years, in addition to continuing education requirements.