I want to replace the vocal song from The Nightmare Before Christmas with their OST versions. The performances differ somewhat and I like the OST ones better. What would be the quickest and cheapest way of doing this for Mac or PC?

So far I've ripped the video using MacTheRipper and then converted it to anamorphic using DVDRebuilder (it was 4:3 letterboxed before). I've tried Womble before, didn't like it very much. Might've been because I had an older computer then. Will be willing to give it another go. Tried iMovie - which read the vob files but the quality looked awful.