Old Girl.

we own a very faithful 1989, 4X4, toyota hilux, 3L, 2.8 D, LN106. the engine purrs like a kitten, only problem is the gear box. only will go into 1st & reverse gears when the engine is stopped. question! as we live in the middle of Australia , Tennant Ck, NT, a long way from major cities, what is the best way to correct this problem. at this time it is unregistered & will require a road worthy pass to register. would be grateful to any suggestions or ideas.