A door from the mid-1970s is old enough that the fix is rarely "tighten this bolt." If the issue is a loose track bracket or a sensor that's gotten knocked out of alignment, those are reasonable for a homeowner to check first - no special tools, no stored spring tension. But on a door this age, a stuck roller or a snapped cable is almost never isolated. The track itself may be bent from decades of use, or the drum the cable winds onto may be worn enough that a new cable just frays again in a season. Springs under tension are not a weekend project regardless of the door's age - that's true everywhere, not just here, and it's the one place we'd tell you flatly to stop and call rather than finish the job yourself.