What to do in order to get into medical school
1. You definately have to take the pre-reqs. Some schools have additional requirements (classes) but the general ones are
1 year of Biology with lab
1 year of Chemistry with lab
1 year of Organic Chemistry with lab
1 year of Physics with lab
1 year of English
Some places require math/calculus/statistics. Other places require Biochemistry. Some require Genetics. Some schools won't accept biology/chemistry/orgo/physics course geared towards allied health/nursing. Others will. Call the school you are interested in to find out.
MCAT is divided into 4 parts, 3 of which are scored numerically (and 1 which is scored alphabetically but no one really looks at the score). The 3 parts are: Verbal, Physical Sciences, and Biological Sciences. The Verbal is similar to the reading comprehension portion of the SAT but with longer passages, more passages, and a shorter time constraint. The Physical Science will test your knowledge of Physics and Chemistry. Calculators not permitted and a formula sheet is not provided so you will have to memorize those physics formula for this section. The Biological Science will test your knowledge of Biology, Organic Chemistry, Genetics, and occasional Biochemistry. Score ranges from 1-15 per section. A combine score of 30 or above is considered a good score. The last section (scored alphabetically) is a 1-hr, 2 essay portion which is given very little weight in med school admission process.
3. Bachelor degree not required. However, admission is competitive, with some schools receiving over 10,000 applicants for 250 seats. Most applicants will have a bachelor, and some will have masters and others doctorates. Although most schools don't require a bachelor, those who do get admitted without a bachelor usually have other outstanding qualities (ie., ADN with 20 years of ICU experience at a tertiary care hospital). Some schools do require a bachelor degree upon matriculation, so check with the schools you are interested to find out their requirements
4. The application process - long and expensive. You will need to apply via a central processing service - AMCAS (for MD schools in the US) and AACOMAS (DO schools in the US). A lot of applicants apply a year before their anticipated start (if you want to start August 2007, you apply starting June 2006). The primary application organizes your personal statement, grades, mcat, extracurricular activities, etc. Then schools will mail you a secondary application upon receiving the primary application. Some secondary application will ask more questions, others will just ask to confirm your information. Each step of the process requires cash. The vast majority of schools require onsite inverviews (Mayo does it by phone). From their interview pools, the admission commitee then decides who to give offers of admission.
5. Foreign med schools - always a viable option but please do your research before deciding which one to go. Some states will not grant permenant licensure to alumni from certain schools (California and Texas comes to mind). Other states don't care. Also, if you want to do certain specialty (that is very competitive), you may be facing an uphill battle as a foreign med school graduate. The one true advice is this: be wary of any foreign medical school that will offer to give you credit or advance standing because you are a nurse/PA/NP/DC etc. Remember, your goal is to become a praciticing doctor. As of today, none of the state board of medicines have yet to grant permenant licensure to anyone who received advance standing from foreign medical schools.
Hope this is helpful.
A few good links to get investigate med schools in the US
As to whether to go for medical school or stay as an RN or become a CRNA or CRNP, etc - that's up to you.