You’ll need to clarify which graphics you want to change.
If you’re changing graphics in the video, then the new graphics will have to be edited into the existing video (probably covering up the old ones using new, full-opacity graphics, to cover the old ones. You’ll then have to re-encode this again for output to DVD. This can yield lesser quality, depending on the quality of the original, but the average viewer may not be able to tell the difference.
If you’re only changing graphics in the DVD menu, then Jeff is right. You can rip the m2v and ac3/aif/wav files from the original and reuse them with the new disc, without losing quality. I’ve always used VobEdit to rip the disc on a PC. https://www.videohelp.com/software/VobEdit
If you’re on a Mac, I hear MPEGStreamClip will do this. I can’t test it right now, as I’m on a Trashcan Mac with no DVD drive.
Good luck!
Chris Sebes
Senior Video Editor
https://www.MediaMixStudios.com
Chris Sebes
Senior Video Editor
http://www.MediaMixStudios.com