Swollen battery - how can I get it replaced?

Hi everyone,

My iPhone 5s (I know, ancient) has the beginning signs of a swollen battery and I'm really hoping to save the phone. Most phone screens give me migraines, and this one, for whatever reason, does not. The phone is amazingly still working just fine aside from the battery issue. Even my backup 5s I have bothers me, so I'm desperate to save my old phone if I can. I don't want to attempt to do it myself but I know it can be done, so does anyone know of a place that will do it? I have an appointment at the apple store tomorrow to make sure this is in fact the issue, but I'd just like as much information as possible in advance incase they won't fix it.

Thanks in advance for any help!!