Same thing happened on my 97' when I tore it down for rebuild. Bent (shifter) selector axis would not let me split the cases apart. Had to cut it!
Steve Beane from Afterhourscycle got me the piece (just the selector axis it self) I needed no problem.
FWIW, it's should be in the fiche at Gofasters, but it is called a selector axis.
Look at the fiche for any year Gas Gas under "shift cam" part #19.