Yes, as long as the tracks are identical in length you can make a substitution. All you do is sweep the song to the vocal, then import the other track.
I do it all the time with midis that I've enhanced the instrumentation. On one file I remove the lead instrumental(s), and on another I leave the lead instrument(s) in.
Then I do as you're suggesting, sweep to the full instrumental, then import the Karaoke version. I usually save both files as I go along, then burn to a cd, one as a demo, and one Karaoke version when there are enough to warrant putting them on a cd.
Works exactly the same using tracks with and without a vocal .
Makes it easy to create a Karaoke file, especially with songs one doesn't know all that well.
George