Earpiece Speaker replacement

If you have little or no experience doing this yourself, and you don't have the tools and steady hands, and you do not want to do an out-of-warranty replacement at Apple and don't care about future service, then locate a reliable 3rd party repair site in your area and pay them to do it. Check what their warranty is.

There is one other possibility given your symptoms, you may have earwax in the speaker. Either get one of the little suction devices like you use to suck mucus from baby noses or use your lips and lung power and such the wax out of the speaker (Many people have done this with AirPods).

Because they do not replace the speaker, they would replace the phone. Not all of the parts of the phone are able to be replaced outright. So, while they can replace the screen, and can replace the battery, everything else requires the replacement of the entire device. The price quoted is the out of warranty replacement cost, which then gets you a refurbished device that comes with the balance of your existing warranty or 90 days, whichever is longer.

Up to you, however understand that if you open the phone, then Apple will no longer service the device. While if you get a refurbished device, then you get the warranty as indicated, and continued Apple support, who will also offer an out of warranty replacement again if necessary.

They take your phone, replace all of the parts and use it for service replacements. They do not just fix the speaker.

Yes. You're reading it correctly.