Secure Image Domain - Have you gone through this process?

We've been advised to secure our image domain in Eloqua. Has anyone gone through this process with live campaigns? I'm concerned about shutting campaigns down while we go through and re-save our assets to update the image domain. When we went through the process of securing our microsites, we had to shut down campaigns for over a week while we updated all the links to landing pages in our various emails and landing pages.

Does anyone know which URLs will be updated automatically, if any? For example, will emails and landing pages created with the builder just need to be opened and saved, or will we need to re-add images to the assets?