For fixed price listings:
You can make changes to your single-quantity fixed price listing until the item sells.
To revise a multi-quantity fixed price listing: You can change the item description, pictures, shipping, payment information, and any upgrades whether or not your item has a sale.
You can change any information on a multi-quantity fixed price listing after a sale except:
Duration
Category
Title
Format
Not sure if that helps you or not.