1) Here's how you track classes, videos, games, or activities not in the tracker: www.sparkpeople.com/community/ask_the_expe
2) You don't need supplements or vitamins as a general rule. A balanced diet with enough calories to support your activity is all you need. You'll need protein, complex carbs, and plenty of healthy fats and other nutrients, but you need that through your diet. A multivitamin can help if you have trouble meeting these goals, but you don't need anything else.
You do need to stay hydrated, and track your calories burned and update your fitness goals. You burn a lot of calories, and eating enough before to support it, and after to recover, is important. :)
Here's a fantastic article series that should help you on high performance nutrition: www.sparkpeople.com/resource/nutrition_art