We disconnect the opener, secure the door with clamps so it can't drop, and release tension on the spring system before touching the cable - that sequence is non-negotiable on any door, regardless of age. We pull the broken cable, check the drum and pulley it ran through for grooving or damage, and replace both cables as a pair even if only one broke, since the other is usually close behind on the same schedule. Once the new cable is seated and tensioned, we run the door through a full cycle, check balance, and reset the opener's travel limits if needed. The one thing we won't do is repair a cable on a door with a rusted or cracked track - at that point the cable is the symptom, not the problem, and we'll say so before we start.