Dracule, You mean "rip" not download. And while Blu-Ray ripping is not a difficult task it's way easier to rip this off the DVD (assuming it has a dedicated stereo layer) because the Blu-Ray has only 16/48k resolution on this disc anyway. Too bad, Blu-Ray audio can be up to 24/192k.
To rip the DVD go to my primer on ripping hirez off DVD (in this case, DVD-Video, not DVD-Audio).
http://www.audiocircle.com/index.php?topic=69151.0