An extension spring under tension will put you in the emergency room faster than almost anything else in a garage. We'll say that plainly: if the spring is stretched, kinked, or has a cable that's come off the drum, step back and call someone. Where DIY makes sense is the small stuff - tightening a loose hinge, lubricating a roller, clearing a track of debris. Where it doesn't is anything involving the spring system, the cable, or an opener that's grinding instead of lifting. We also won't pretend every job is a quick fix. If the door is original to a 1969 build and the track is bent along with the spring failure, replacing the door is often the honest answer, not patching hardware that's outlived its design life twice over.