disconnect cables at selectors on g.box and see if this frees up the gearlever,if so,there are two needle roller bearings in selector mechanism on g/box which seize up causing problems you describe,remove the six 10mm bolts holding on the selector cover on,disconnect rev,light wiring and remove the cover,inside here are the bearings and you also need the top oil seal,strip down taking careful note and rebuild with plenty of grease and lubrication on the selector shafts,hope this helps,good luck
cdc
November 2010