so when you send it to the manufacturer, they will only do a full repair on the device. (if there is damage to anything, regardless if the damaged parts are functioning or not. they will not do a repair to function, but a repair to "like new" this is why they need to replace all those parts.
check to see if the earspeaker works in call. if both the earspeaker, as well as the loudspeaker are not functioning, it is more likely a problem with the Audio IC, in which case, there would be a further problem than just the speakers.
you can try to replace the loudspeaker if you get the part, but there is no real guarentee it will fix the problem, without actually getting inside the device and running tests on it.