This thread is far off it's subject of replacing truck fleets, but ...
The CAF has been making things work with too little of equipment that is too old and worn out, and the CAF has been doing it for so long that people perceive their improvisations as being what right looks like. The CA is buying new vehicle fleets and it must ensure those fleets are reliable and maintainable at the tactical level in a warfighting context.
If you are a battalion or a brigade, and you are rebuilding engines to keep your fleets operational then you are not war fighting. Easy, fast, and simple parts changing is what needs to happen in the war fighting units and formations. And if your vehicle fleets are reliable, durable, and maintainable with parts swapping for warfighting, then those vehicle fleets will be reliable, available, and maintainable via parts swapping even in unit lines back home.
A PRes Plattalion or Tregiment of 50 pers should not be squandering its limited human capital into exquisite skill-sets unrelated to its assigned mission task so that the unit can locally rebuild engines and other major sub-assemblies. Not only should it be unnecessary to support a fleet that is reliable, available, maintainable, and durable - but doing so also teaches lessons / muscle-memory in relation to combat maintenance.
The UK (and I think specifically the British Army) did a study in the past few years which determined a whole lot of things, which NATO armies assumed they would get from contractors during war, will not be available to contract in a time of war ... sort of like we are seeing with many types of munitions today. The sudden spike in demand will exceed industry capacity. While I don't believe a manoeuvre unit, brigade, nor even division should be doing such levels of maintenance, I think CA (or CJFC) should maybe possess a deployable theatre level capability.
This story lacks so much details, it's not even a good anecdote to make an argument. Who is "we"? Where & when was this? Why were you struggling to keep trucks from being grounded? What was the USNG unit and what was it battlefield role?