If you're not sure about the information that needs to be on the return label, then I would call Customer Service to be sure before you send anything back.
I can tell you from my own experience with returning something back to Walmart that was purchased using their online service and using a print-out label, you need to leave anything that has a barcode on it for the USPS.
The Post Office needs to have the bar code so that they can scan the item and use the information that's in it.
With Walmart, you have the option of returning your item either by the Post Office or by FedEX, and both have their own separate bar codes on the label and you need to use the proper one.