Class Interaction- My high school class was about 295 people so this will be like returning to high school for me as well.  I expect there to be diverse backgrounds and interests represented in our group so I am not afraid of us being homogenous in spite of our common bond in medicine.  Therefore, due to the varying personalities and connections, I do expect our class to break into smaller groups.  Some people will probably never show up to class, studying solely on their own, and I am not sure how that will affect their social interactions with the class.  Others will show up all the time.  Because of the increased pace of the class, I think social situations will evolve more slowly as we will all be so busy.  Though I do not have a problem with smaller groups forming, since I believe that is natural, I do fear that they will become cliques.  The main way to avoid that is by not acting selective yourself, which is easier said than done.
My class role- I want to be the guy who is approachable with a pleasant spirit and ever-present sense of humor.  I want to know almost everyone's name and stay on cordial terms with everyone I meet (not necessarily good friends but at least on pleasant terms).  I feel like I have achieved this in college, and I would like to duplicate this in medical school.  In return, I would like to use the disarming nature I have established to allow me to be accepted into every group in our class (i.e. I can sit with anyone in the cafeteria).  That way, I can ask questions from people when I do not understand the material and will try my hardest to help people out when they seek my help.  In this way, I will have turned a potentially uncomfortable, unknown environment into one that is inviting and not as intimidating (that is until test day 

 ).
UTSW Research- Definitely call Dr. McPhaul.  He sounded like he was very willing to help any students do research who showed interest in it.  I am sure that he could answer your questions.  Do have a few ideas in mind as to what areas you prefer or even specific projects if you notice one you want.  That way, he can get you lined up with a researcher.
Studying- In the past I have leaned toward the slacker side, but I can kick it into gear when I need to.  I have a feeling that the environment of medical school (not being on a college campus, surrounded by other people who are working hard) will drive me to work hard.  Also, fear will push me to not let my guard down and relax.