The .dvd files are just standard .iso disk images, so I guess you just need something that can mount an .iso in kubuntu as a "virtual" drive like poweriso in Windows, and then you will be able to play it from there as if it were a disk...
Transcoding is not an easy option, btw, as this is an image of a DVD rather than a serial video stream, so you would have to pull out just the main feature from the VOB files (after mounting it anyway) then transcode those, and that would take a very long time....