A broken extension spring looks like something you could swap yourself, and on some doors you could. But a door under tension that lets go while you're working underneath it can put you in the hospital, and on a 1970-era door where the drum, cable, or track hardware may be original, there's a real chance the failure isn't just the spring - it's a bracket or a cable that's rusted through underneath it, especially after decades of the cold-band winters this county gets. Our honest limit here: we don't sell spring kits for do-it-yourself installs, and we won't walk you through it over the phone. If you want to inspect the setup yourself to decide whether it's worth a call, look at whether the spring runs along the horizontal track or wraps a bar above the door, and whether the cable looks frayed or rust-pitted. That tells you what you're dealing with before anyone touches a wrench.