My advice: Take it slow. I know that gaining acceptance to med school (or other professional programs) is the main goal of most people entering the program. In the short term your goal should be to do well in the program and make yourself as competitive and well rounded a person as possible.
Some of the tougher courses are Cell Pathology, Mol. Med. of the Heart, Physiology, Topics in Neuro (Dr. Ingoglia is a treasure), Stem Cell Biology. Taking these courses and getting A's in them will prove that you can handle the work load. However, many students take these courses (and MGM) thinking that with a little bit of effort they will get an A...not true. You have to be consistent in your studying (just about every day) and be able to deal with mountains of information. In my opinion, I think it's better to ease into the program and not take MGM right away, but again many of you want to apply right way and having a good grade in MGM can really set you apart.
A quick not on why UMDNJ doesn't keep statistics: Every student entering the program does not want to go to med, dental school, etc... Many students want a masters to teach, work in pharmaceuticals, research. Also many students who enter the program decide that they would rather pursue a PhD. So if the school accepts 100 new masters students and only 5 (hypothetical) get accepted to NJMS that doesn't tell the whole story. Students who finish the program and have a competitive MCAT score often have multiple med school offers and some choose not to go to NJMS (I myself know many people who have gone this route). The school would then have to rely on those students contacting UMDNJ to let them know where they are going (not an easy task). Lastly, many programs have high success rates, does this include students who have had to re apply (once, twice?) and students who decided that their only option was to go overseas?
It is a stressful time and many of you want specific answers. The best advice you will get is this...work hard, get good grades in the program (>3.7), try to have a competitive MCAT (average at NJMS I think is 32), be well rounded and interesting (i.e. pursue your own interests outside of medicine), and be confident in achieving your goals.