A straight opener swap - same mounting points, same rail length, no header rework - runs about two to three hours once we're on site. Add a keypad, a smart-phone module, or battery backup, and figure closer to three and a half. Where it runs longer is on houses from this same 1988 wave where the original header bracket was installed for a lighter, shorter-rail unit than what's standard now; we sometimes have to add blocking or re-anchor before the new opener goes up. We won't know which situation you've got until we're looking at the ceiling, so the quote we give on the phone is a range, not a fixed number, until we're standing under it.