If the image is the same size as the old one then...when you get the new one.
Copy the old image to the desktop (for safe keeping)
Open then old image (the one in the job, not on the desktop) in Photoshop, also open the new image, so they are both open. With the new one active,
Select all then
copy then make the old image active, then
paste and position the image where you want it.
Once ok, then flattern the layers and save the old image (which now contains the new image).
Then simply update you images in Quark
Doing it this will insure that the image remaines in the exact position as it was before...
simply renaming and updating may result in image shift, which means you will have to check every single image.
Doinf it my way will keep everything the same
Marcus