The difference between an air dive and nitrox is..... nothing that you would notice other than Maximum Operating Depth and longer NDLs - which is what you will learn in a class.
Nitrox is not a mystery anymore - that said if you are still fairly new to diving - I would take a nitrox class and I would wait on the shark dive until you think you are comfortable diving and have your skills squared away.
But if you want to do the dive and you are confident you are ready - then by all means jump in with both feet and don’t worry. Nitrox is the least of your issue with a shark dive... :-)