It will be very difficult to remove the piano from the track without ruining the rest of the song. you try EQ-ing the piano , but since piano has very wide frequency range (probably the widest of all instrument) it will be difficult since you will probably have to EQ every second separately. by the way how many instrument there are in the song. if its just piano and vocal, you can easily remove the vocal with extremely good results. If there are other instruments, maybe you can get MIDI file of that song with only the music, run it through proffesional music making software (cubase) ans save it as wave, and then mix it with the vocal you've removed from the original track. and does the piano bother you that much?