I used to work for a defense contractor in the late 80's, and my job was to build "spares kits" for our products -- every component in the system had one or more spares that were packaged up and sent along with the equipment so it could be repaired in the field. I assumed all military procurements still worked this way, with enough spares and/or documentation to do field repairs.

Though this product was relatively easy to repair, it was mostly discrete circuit boards plugged into a backplane. Most of the components were socketed and could be easily replaced if needed.