Can I replace image files without Coppermine knowing?

[the Fiddler]

Sorry if that subject is oddly worded.  I'm kinda new to this stuff and am not sure how to ask what I want to do, so let me explain.

I want to download all the images from my Coppermine gallery (400+), then run them through Photoshop to resize them to say 75% and resave them as smaller files.  I want to do this to save some web space as they're taking up nearly a Gig on my server.  I know how to do the local stuff, but if I do this, then re-upload over the top of the existing files with the new smaller ones, is Coppermine going to know?  And will it then screw everything up?  Or is there a way to tell it to update the file info (like resolution), but without loosing picture names, comments, ratings, etc. associated with each file.

If I'm not clear on what I'm wanting to do, let me know.  Thanks in advance for any help.

[Hercules24]

I once did it the other way around: re-uploaded bigger images
Under admin tools there's this function: Reload file dimensions and size information
It works perfect.