Odds of Getting In
Getting into a Ph.D. program or into medical school is a challenge. If you can score a thirty-nine or better on your MCAT, then you'll have a ninety percent chance of getting into med school (source). The top Ph.D. programs only accept seven to ten students per year, so your GRE had better be impressive if you're going that route.
Once you're working in the field, it's important to be active. If you're researching, you'll want to publish early and often. If you're practicing, the next step will obviously be to find a job. People say doctors are always in demand, but that's the case precisely because it's so difficult to complete the training. If you can do that, though, you should be able to find yourself a gig in your field.