When I update my account via OFX, and it imports the transactions, there are often times it gives an incorrect label to the transaction. It will assign REI to both Harbor Freight and O'Reilly's auto parts transactions. I can see why it does this partly (both have REI in them), but I don't know how to correct the behavior. So how do I fix this, and stop it from doing this in the future?

Have you checked the settings of the payees? There is a setting you can tweak for payee autodetection