300 e gearbox prob

[tractorboydavid]

While heading up to newark on the a14 the gearbox on my fathers 98 300 e diesel dropped out of gear after leaving it for 10 mins it will move for around 20 seconds before loosing drive it will not select any gear have checked the oil level and the filter but prob still here HELP Also when turning off engine B A S comes up on the dash any ideas am gettin nowhere fast