They'll do it, it's best to call and see what they have in stock. Whenever I've made appointments I feel I've waited longer than when I've walked in.
You can walk in, the wait is usually about 10-15 and they should have a retainer for you and they will put it in.
You should be able to just walk in to do it. Appointments are for piercings and not for jewelry changes. Anf yes they'll help you
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