The aircraft was making a landing approach to Sydney when the pilot observed the nose gear had failed to extend normally, after the landing gear was selected down. The aircraft was diverted to Bankstown where it was subsequently established that the nosegear trailed about 20 degrees from the locked down position. All attempts to extend the nosegear were unsuccessful. The aircraft was subsequently landed on the 36L grass strip. During the landing roll the nosegear collapsed and the aircraft settled onto its nose. Prior to making the approach and landing, the pilot said he had shut down the right engine and feathered the propeller, which was then parked in a horizontal position. On short final, the left engine was shut down and the propeller feathered. Insufficient time was available to park the propeller, which struck the ground in a vertical position. This resulted in the left engine crankshaft being fractured, at the rear of the propeller hub mounting. It is considered that the nosegear failed to extend following the failure of the aft rod end of the nosegear aft retract rod. A subsequent specialist examination determined that excessive forces were imposed on the rod end due to landing gear misrigging, following replacement of that component during a recent maintenance inspection. The aft rod end subsequently failed as a result of continued overloads.