Appt not necessary for most things since there is a repair person there most of the time for minor repair like tune ups. For anything more than that I think best to call and let them know the problem and for an appointment.
Not if you drop it off for service. If you need the bike ASAP then call and ask of they can give you priority service. If its a small repair/adjustment it is likely they can do it for you on the spot. Of course major repairs or component replacement will take time.
I have walked in with my kids bikes to get the tire checked. Give them a call.
Good question. Perhaps a call to the retail outlet you plan to visit would answer that question. Just sayin...
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