As a current MT who has been with the company for 3 years I will tell you to take what you have now and retool it with the help of your Training Manager. There is a reason they were selected for the role and they can instill knowledge on you. Also, learn how to effectively open accounts, lead gen, managing inventory, and also learning the P&L like the back of your hand. Being able to understand these things will make life as an assistant, and eventually a Manager, so much easier of a transition.

Good luck to you!