Alternatively, there's a torrent (ape+cue+log) that contains the complete 2-Disc soundtrack. From what I could gather. after listening to the entire album, is that it has every last song that is in the game, unlike other OSTs. The sound quality is superb, considering ape is lossless, but the prodution value is high.
I'm using the Wii Internet Channel and can't link to anything right now. If you're interested, and I get the free time, I can find that torrent for you. If you can't wait that long then go to FFShrine Forums, signup to access links, search for Super Mario Galaxy Original Soundtrack (lossless) and hopefully you'll find it that way. Hope this helps.