How long does it take to Replace early 2011 Battery

I have a warranty with apple I have a early 2011 mackbook pro.I keep getting Service battery under my battery icon.Apple Store is about a hour and half from me.If I drop it off Can they replace the battery same day?I was told sometimes they don't have batteries in stock on the apple chat.

rgarjr said:

swapping a battery should only take about 15-20 minutes.

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Thanks