slave cylinder

[new gas gas]

my brother was on my ec 250 and had to stop so pulled clutch but the slave cylinder seal must have went as clutch did not work and he slammed on back brake engine cut out and back wheel locked up now it wont go in to neutral and if you do get it in and start it up it runs for a few secs them seems to jump in to gear and if you push it in neutral you hear a crunching noise then it seems to jump in to gear as back wheel locks up some one told me gear selector maybe gone or gear box is damaged any ideas and is it difficult to change gear selector