Upgrading with modified Modules files and Customized Theme files

I modified files in the Modules directory such as:

footer.ascx
infoblock.ascx
header.ascx

After I install an upgrade from 1.4 to 1.5, do I simply upload my modified files into the proper directory?  Or do I need to use the V1.5 file and recreate my edits in the new file?

In other words, are these sorts of files interchangeable from version to version?

Thanks
Sue

I would open the new files and copy over the changes from the old files.

Thanks, as always for your speedy response!