Stela,
It sounds like you should buy Microstudio to convert your karaoke disc into either bin files or KMA files. (I use KMA files because I run Hoster) so you can run them on your computer. Buy Vogone to remove the vocals and buy KHpro to create your own CG+G disc. Download the demo copies of the programs and make sure they work with your cd/dvd burner.
MTU has a package where you can buy all three programs with Keyright which will let you change the keys of your of your karaoke tracks.
I suggest the
Karaoke Suite 4 for $139.99.
http://www.mtu.com/basics/karaoke-suites.htm
I Hope This Helps
Jim