If you actually like to receive the goods you buy I'd suggest not to buy from this vendor (just search for RichardMastny on other boards and you will get the idea....). I still have one of his "modules" sitting at home and I think a 3 year old could have done a better job putting it together (and it probably would have even worked ...).
If you want to play DVD in stereo using the TV tuner module as your AV input (there's also an option which allows you to drop the tuner all together) I'd suggest to use the AUX input for the sound/stereo input (use the AV inputs of the TV Tuner for the DVD AV) and buy the switching module from TVonNAV (
http://www.tvonnav.com/ ) which allows you to change the audio source whilest being in TV "mode".
I have installed this setup in my X5 and it works perfectly. You can find some addtl information at
http://www.janixworld.com/x5/AUX_Input/
Hth,
Jan