Swapping a remote battery or reprogramming a keypad - that's a fair DIY job, and we're not going to tell you to call us for it. Where it stops being a good idea is anything involving the opener's travel limits, the force setting, or a chain-drive unit that predates safety sensors entirely.
On a house built around 1979, there's a real chance the opener has no working auto-reverse function, which means a motor that doesn't stop when it meets resistance - a child, a pet, a bike. Wiring in a sensor kit yourself on hardware that old means matching wire gauge and terminal types that don't match anything sold today. Get that wrong and the opener looks fine until the one time it doesn't reverse. That's not a scare tactic, it's just what original 1970s hardware is missing by design, and it's the one place we'd tell you to skip the YouTube video.