Apple

So my wife's Series 5 Apple Watch is now at 78% battery capacity and she is complaining. I assumed BAHHHHHH EFFF APPLE when I saw $99 battery replacement, and was starting to shop for a new Apple Watch for her on Black Friday sales.

BUT I stumbled across this site and see that perhaps when people do this battery replacement Apple isn't actually opening their unit, but just sends them a new one? If so then do you think we get a brand new Series 5 back or would it even be a newer one? If I am wrong, then should I buy her an SE or what should I buy for the cheapest price that has the same function or better than her current Series 5?

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THANKS!