A torsion spring under load can put someone in the hospital, and that doesn't change based on how old the door is. If the fault is a spring, a cable, or anything holding tension, that's not a weekend project - call it in. Where we'd tell you to hold off calling is something like a loose bracket you can see and reach with the door down and the opener unplugged, or a track that's visibly caught on debris. Tighten what's obviously loose, clear what's obviously in the way, and if the door still binds, that's when it's a call.
On a house with 1968-era hardware, the extra risk of DIY isn't just the spring tension - it's that replacement parts bought off a shelf for a modern door often don't match the tolerances on older track and drums, and a mismatched part installed under load fails worse than the original problem.