If your gear change cables are not broken and still attached to the selectors on top of the g/box then I would have a look at the selector housing on top of the g/box,in there is a roll pin which is bad for shearing and you lose all gears,you have to remove the air filter housing and hose to the turbo,breather pipe and reverse light sw.wiring connector,can`t remember if the g/box top mount has to come off but it may free up space to work in there,remove the two gear change cables and the ring of bolts on the housing and it should lift off.If the roll pin is sheared then I don`t know if you can get this part now and you have to take the whole housing assy. which is very expensive so a trip to a scrappy may be worth a visit.Good luck
cdc
February 2013