Actually, Pat's experience tells her that if you build it wrong to begin with, it will stay wrong forever because if you can't take the time to fix 10 things now, you certainly are not going to take the time to fix 50 or a hundred things later. And managing the poor design will grow to be your singular job or simply be abandoned when you realize you can't fix it. Then you'll blame Access rather than your poor schema.
There is a difference between "not great" and "not workable". Poor naming practices are "not great". They will cause typos and errors but if you have properly defined Option Explicit, at least you'll find most of the errors if you bother to compile. But novices rarely bother to compile. Poor structure is "not workable".
While I agree with
@JMongi that the app doesn't have to spring forth as perfect and complete but if your company is making business decisions based on it, you'd better not be giving management wrong information or you could single handedly bankrupt a company.
It is far better to identify your single worst problem and work on solving that. Make the scope as small as possible. You are doing everything manually now. Automate just a little bit at a time while you get your sea legs. If inventory is your worst problem, work on solving that. But, keep in mind that inventory is one of the more complex "simple" processes. I call it "simple" only because when someone says "inventory" most people can at least visualize it generically. It goes downhill from there. This is not an inventory of widgets. It is an inventory that requires using "part" of something and managing units of measure and expiration dates. If you purchase by the gallon and use by the quart or pound, you better know how to do the conversion accurately. You also need to understand that updating quantities is not the way to manage inventory. You need to do it with transactions. Record what you receive from the vendor. Record what you add to a batch. Record what you discard because it is expired. Add up all the transactions and you know what you have on hand. When you Record what you add to a batch, you need to understand how to pull from the oldest, "open" inventory bucket. Otherwise you will waste material if you allow it to expire.
Adding columns to existing tables doesn't break any existing objects. Adding new tables doesn't break any existing objects. Having to split a table into multiples because you didn't recognize repeating groups or understand normalization breaks EVERYTHING.