You would want to call ahead to make sure that the shop has the replacement battery in stock and ask them for an appointment time, so that they understand that you will be waiting for the service to be performed.
It will only take about 15-20 minutes for the technician to replace the battery, so you might bring some reading material to use while you wait.
Recently, I visited a shop......without an appointment.....and it only took about 30 minutes for the battery replacement process. Most shops understand that you want to get in and out as quickly as possible for simple service.