TMPEnc DVD Author - How to re author but no loss in quality?

Hi Everyone.

I've got a live (None Copywrite) DVD file on my harddrive.It has chapters bu no start or chaper select screen.

I have TMPEnc DVD Author and want to use that to Re-Author the DVD files.

I want the files to be exactly the same quality in both video and audio with no loss at all while re-authoring.

Do I need to do anyhing to keep the quality lossless or using his program will it automatically keep the new re-authored DVD the same quality as the original.

The Audio of the file I want to Edit is 256 kbps and he Video Varies from 3-6 Mbps.

I do noe have na AC-3 plug-in for TMPEnc,but that won' matter,will it?,as I don't want to re-encode the sound.

Thanks,
Ian