Good morning!
There is currently no way to edit the item description or the marketing tools. Maybe in the future.
However, you can edit the Seller Details using the Find & Replace functionality. You would create your new Seller Detail profile, save it, choose the listings you want to replace with the new SD profile and use the Bulk Find & Replace to complete that task.
Same instructions apply for the Shipping and Checkout profiles which can also be edited using the Find & Replace. Make sure to create the new profile first.
Hope that helps -
Cara