There's a limit to what we'd tell anyone to tackle themselves here, and springs are it - torsion or extension, on a door this old, the stored tension can put someone in the hospital, and we won't talk a homeowner through that over the phone. What you can check yourself: whether the tracks are visibly bent, whether rollers are cracked or missing, and whether the door is noticeably heavier to lift by hand than it used to be, which usually points to a spring that's lost tension rather than one that's fully gone. Lubricating hinges and rollers with a garage-door-specific lubricant is safe and worth doing every six months or so. Anything involving the spring, the cable, or the drum at the top of the track - leave it. On an 80-plus-year-old door, there's often more going on behind the bracket than it looks like from the garage floor.