I had never heard of this accident before, pretty shocking. Did this discourage more civilian operators from using Chinooks?
Yes, killed it's use stone dead in the North Sea ISTR. Amazing that anyone survived the crash.
The report doesn't indicate the existence of a 'Military Gearbox', only different modification standards, the change to -6 being the important one in the accident report.
Assumption that modifying the nature of the mating surfaces would not change wear patterns at those surfaces was an error. Underestimation of the acceleration of corrosion due to salt laden air was also a big factor it seems.