Can I take a stereo wave file in realband and extract the instrumentation as separate individual wave files? If I can where would I find them?

No, it does not do this

You can find Multitrack karaoke/backingtracks on the net if it is a cover song you need.

https://www.jamkazam.com/landing/jamtracks/bruno-mars-uptown-funk

http://songgalaxy.com/

http://www.tracksplanet.com/multitracks/songs-songs1/

http://www.karaoke-version.com/custombackingtrack/karaoke.html