Starting Inventory Values not Correct

Before hiring me, my client tried to handle inventory. Result: hundreds of inventory items entered into QBO inventory via a spreadsheet import; that is - they all have an Inventory Starting Value of whatever the quantity at the time was (usually one item, but sometimes more). The client didn't create purchase orders and link them to bills or checks to properly receive inventory. In the meantime, pretty much all items that were imported into QBO inventory have been sold. Is there a quick fix that I can make to accurately reflect the existing inventory, cost of goods sold, amounts owed to various vendors, etc? Or are things hopelessly out of whack?