there are "learn in" procedures for the control handle that someone with training will need to do.
It may be something you have the physical ability to do, but this is like asking a 10 year old to clean a loaded gun, or capture a live shark, rabid dog or alligator without instructions. We kill about as many people every year by animals or by gun cleaning accidents as we do with forklifts, in the USA.
This really is one of those spots that having the tech who did the diagnosis to be who is responsible to insure the job is done correctly. Since it was determined to be a 'high dollar' part, your boss would be far more penny wise (and -not- pound foolish) to expect the troubleshooter to stand behind the diagnosis.
When this truck "randomly shuts down" does it show ANYTHING in the dash? no codes? and you can always turn the key off and on again to get it running? and it runs fine after cycling the key switch?
If you had me doing this troubleshoot, and I had no idea of the history of the cable in the mast, I would suggest the most likely places for this 'Weird Intermittent Failure' (WIF) to be the mast cables, as they twist and bend more than any other cable on the truck, and can break the cable conductor internally but not break the insulation. but if you have NO codes, then I would be looking at the key switch.