This has to be one of the most asked audio questions on the internet (this forum included). If you have to ask it again, you haven’t done any research into it, at all.
Unless you’ve got the original recordings (masters), it ain’t gonna happen. The best you can hope for is lowering of the vocals, and if you try to go too far with it, you’ll begin to lose some of the stuff that you’re trying to keep.
Save yourself time and anguish, by buying a karaoke version of the song. You might even get by with a midi version. There are programs available to change the instruments used in midi files, which can yield surprisingly good results (certainly better than what you’d end up with, by the time the vocals are completely inaudible).
Of course, I’m assuming you have taken the appropriate steps to securing permission to use this piece of music.