Most of the problems occurred when techs put wrong oil in DCTs. It's not rocket science, but you need the correct procedure. Tranny has both fill and drain plugs, just like 6MTs, so no problems there. Easiest way to do it would be to carefully measure what comes out and put that amount back in, but that requires no leaks during the drain
.
You're going to get a million replies saying 'follow the manual', but you're smart to know no fluid is going to last the life of the vehicle... unless you want the life of your tranny severely shortened
, especially when car is getting tracked. Good luck man.
EDIT: Noticed topping off procedure is listed above; that's all you need. Drain, fill, then top off. DCT has no converter, so it's like a manual tranny in that regard. Good luck.