Does a mistake in the wording of the Tashahhud, and correcting it within the same Tashahhud, invalidate the prayer?

The prayer is not invalidated by an error in reciting the Tashahhud, as long as the worshipper returns to correct it. There is no blame for the error, based on the Almighty's saying: "Our Lord, do not impose blame upon us if we should forget or make a mistake."