A straight swap - same bracket position, same rail length, new motor head - runs about the time it takes to disconnect the old unit, test the new one through a full open-close cycle, and set the travel limits and force settings. Jobs with a low-headroom mount or a jackshaft conversion, which we see more often in Placentia's 1970s tract garages than in newer construction, take longer because the rail and mounting hardware have to be fitted rather than reused.
We don't quote a number we can't back up without seeing the garage, but the four-mile run from Fullerton means we're rarely the reason a job runs long - it's almost always the bracket work, not the drive time. If a part has to be special-ordered because your unit is an older or discontinued model, that adds days, not hours, and we'll tell you that up front instead of after the fact.