I think that people tend to approach learning jazz the same way they approach learning other stuff, which is by learning tunes, and this doesn't really work, at least not at first. You have to listen to a lot of it (I'd suggest mike stern for guitar, herbie han**** also has great fusion/funk, piano player) and be familiar with how it sounds. Then get to learning jazz voicings instead of the ones you are probably used to now. You should also get to learning arpeggios and scales that come up in jazz. To play good fusion you need a strong straight ahead jazz background. Buy some books if you aren't taking lessons.
If you absolutely must learn a song, try Chromozone, its in the real book, mike stern.