Reauthor DVD by replacing VOB files?

Hi, this is new territory for me so please help if you can.

I have an old DVD that I authored with Encore. The original project file has since been lost. I now need to replace a few of the short video segments with improved graphics on the video. I ripped the DVD with DVDShrink and the folder contains all the individual VOB files (as the training segments are short). I thought that it would be a no-brainer to replace the 2 VOB files that needed changing, then re-burn the folder with Nero. Somehow it still burns the old video segments.

Any advice on how best to tackle this project? A better program for re-authoring a pre-structured DVD?

Thanks!