Can I replace the talk speaker?

There's 2 mics. A lower one when on a regular phone call. And a Speaker mic when on speakerphone. They both require a new mic to be soldered on or by using a rework station to replace the old mic.

This is the mic you would need for the VN220 whether it be the lower mic or speaker mic.

Though for the speaker mic, you can replace the upper board which has a new working mic on it, or of course solder off the old one and replace it with a new one.