Q: Can a cover image be swapped out of an existing fixed-layout EPUB?

Can a cover image be swapped out of an existing fixed-layout EPUB without having to open ID CC and go through all of the EPUB3 prep steps?

I recently had a book distributor attempt to upload my EPUB3 doc to the iBooks store and it was rejected with an error message that the cover jpg dims were too big. My monthly ID CC membership is done, and I'd like to avoid having to renew it just to change out the cover image, if possible.

Thoughts appreciated!