A garage door cable under load is not a DIY repair, full stop. The reason isn't the cable itself, it's the spring tension sitting behind it - extension springs on older South Amboy houses store enough force to break a wrist or worse if the cable comes off while you're standing under it. If you see a frayed cable, the safe move is to prop the door where it is, unplug the opener so it can't cycle, and leave it alone.
What you can reasonably do yourself is the inspection: look at the cable where it wraps the bottom bracket and where it feeds onto the drum, and if you see rust bloom, kinking, or individual strands starting to separate, that's your sign to get it looked at before it lets go on its own schedule instead of yours. In this region's cold-and-severe climate, steel cable strands corrode from the inside before the outside looks bad, so a cable that looks fine from six feet away can be down to a few strands. That's the one thing worth checking yourself - everything past that point is a job for someone who's unloaded spring tension before.