Last I heard, Seoul would be overrun in 3 days.
I doubt Seoul would be overrun. Horribly battered in the first 30 minutes, yes, but at that point the NK border & several miles north would be carpet-bombed to a pulp along with much of Pyongyang, and the remaining NK troops - largely emaciated - would be facing their own invasion by well-fed well-equipped very-angry SK & USA troops.
More like Korea would be reunified in 3 days.
N Korea has moved landing craft carrying special forces.