I did my own oil change at 1400 miles just because I got into the habit of doing that with my BMW M cars.
I personally don't have much faith in the dealership oil changes - those tend to be done by the newbies, or as Mr. Duck put it, the drug-addled high school drop outs who just got promoted from wash boy after 35 years of dedicated service. Yeah, I elaborated slightly. The issue for me is that they see so few CT5-V BW, they are likely to not know about the special oil, or the quantity required. And if I do it myself, I get to check out the bottom of the car and see if anything is going on. And I know that the filter and drain plug won't get over-tightened.
As for track prep, I second the suggestion that you want to do a brake fluid flush right before the event. High temp fluid is a plus, but getting fresh stuff in there is the most important.
If you continue to track the car, then a differential oil service would help prolong the life of that expensive item. I don't think one is necessary before the event.