Hi,
In answer to the 1st question, you can delete old, unused, stored photos from the Manage Images page. Use the check box at left of photo and Delete button.
I'm not exactly sure I understand the 2nd question, but if you are attempting to reuse old Saved Listings, just use the "Remove" under each photo in the Image Selection section of the one-page lister and then add the new photos by clicking on Select An Image.
Danno