Cool, Customs should be a lot of fun. If my memory serves correctly they try and match up your group with other people in your department/major, so you might get a chance to meet some other aerospace folks. Be advised if you turn in your lab form in person it must go to the Flight School building out at the Murfreesboro Airport, not the Aerospace Department on campus.
That's great you've got a head start on the Diamond! Sounds like a way cool way to spend the summer. When I did instrument the hardest part was honestly getting to know the G1000 and how to make it do everything you want. I believe about half of our fleet has the GFC700 autopilot, which you'll get a chance to use during training. The other half has a KAP140, which can be a bit finicky, but not too bad. I've flown the Diamond as well as Cessna and Piper and really the only difference I noticed was a bit more float on landing. The thing will really glide, heck, I think its design came from a glider. Besides that, the only other thing I had to get used to was having a blue lever and setting the engine on manifold pressure and not RPM.
Another suggestion I would have is studying for the written exam. Many flight students seem to put it off until the very end of the lab and only then begin studying. If you can start practicing some of the questions like distance/time/fuel calculations and learning some of the more "memory" items like sensory illusions, weather info, and regulations, then you'll have a much easier semester!
AOPA is a great resource and has many informative articles for training! I know the flight team is always looking for new members and I know they're always looking for motivated members! If you're interested you can check out
NIFA which is the organization that our flight team participates in. I think they also have a Facebook group.
Good luck and enjoy Customs!