Transition from Quickbook desktop to Quickbook online Plus

We have had someone in our company using  Quickbooks Desktop for a few years now and want to transition to Quickbooks Online. I will be taking over on QBO. However , as I'm going through customers, vendors, chart of account and transactions,  I realize that all of these things have been customized by the user that only makes sense to him. For instance, instead of listing only 30 products we sell and creating  30 pricing rules  for each customer  (We sell products at different pricing for certain customers) he chose to create 30  new products under a slightly different  name for each customer. Thus creating thousands of products listed under our product list for the 200 or so customers we have. I realize that might be hard to follow, but I'm wondering if I should start clean and completely start over in QBO or import information from QBD and individually edit and make heads or tails of each one. Our Fiscal year ends in June . Also, should I change over to QBO at the end of June or wait for the new Calendar year to start?