If the door is only slightly off and still moves by hand, you can sometimes walk it back onto the track yourself - open the door most of the way, support it, and gently guide the roller back into the rail. What you shouldn't do is pull on a bent track to straighten it while the door is still under spring tension, and on a 1938-era door with old, possibly fatigued springs, that tension is unpredictable. If the door won't budge or you hear metal grinding when you try, stop and call it in. That's the honest limit here - track work on old hardware is worth doing right the first time, because on doors this age, forcing it usually means replacing the whole rail instead of one section.