I'd just use the THX optimode on any THX mastered DVD to start out with. Try it out ... see what it does ... get a better feel for the process. If you want to learn more ... then go buy the DVE disc after that.
DVD on the 360 is not usually considered the epitome of image quality. The playback platform just is not very strong. You get an image ... but little else in terms of quality DVD playback.
(Unless this is the HD DVD add on player)