Hi Scott,
I'm sorry to hear that. The process I described above can only be done from your Manage Images page so you did not miss anything when looking for this option in your saved listings. If you are unable to locate the images in question on your Manage Images page for whatever reason, you would need to take a different approach.
If you are only able to find these images in the saved listings they are attached to and not on your Manage Images page, you could still replace the images you would like to swap out by uploading the new images during the process of revising each listing via the following process:
1) Locate your listing in your Saved Listings folder, make any necessary changes (swap unwanted images for new ones), and save.
2) Click the "<HTML> icon to the right of the item on your "Saved Listings" page
3) Select All and copy the html in the popup window.
4) Locate the item on eBay and click the "Revise Item" button.
5) Scroll down to the "Description" section and then click the "HTML" tab above the description editor.
6) Delete the existing description HTML, paste the copied HTML in its place, and save your changes.
This method admittedly requires a bit more effort that the “Replace” option on the Manage Images page, but it should still be sufficient to get the job done.
-Mike