With a 3.3 you can get into SMP program @ Boston MAMS or Georgetown SMP assuming that your MCAT is competitive (> 30 MCAT). I would not suggest taking GRE because it served little or no purpose, an MCAT can be use to subsitute for admission requirement.
In terms of post-bac, there are two types. One for career changer (i.e. high GPA but have not taken science courses required for medical school) and the other one is aimed for minorities and/ or economically disadvantage. Majority of the structured post-bac have a good chance of bringing students into medical school.
Check out the respective post-bac thread, such as CA Post Bac (good acceptance rate to CA med schools), Scripps, etc. They are typically very competitive in general and look @ the whole applicant: extracurricular activities, volunteering, etc.
Good luck.