I agree with difficult...OTL, it was nearly impossible to get the Japanese to surrender! Tactically the Japanese fought until nearly the last man, Strategically much of Japan was willing to fight to the bitter end. While I wonder about whether Japanese Civilians were really going to fight with bamboo sticks like the Army wanted against the US army, and that part of this might have been a desperate bluff by the Japanese to have some kind of negotiated peace instead of unconditional surrender (a major sticking point was the role of the emperor in Postwar Japan--as essentially the key religious figure of Japan this really had that level of importance to the people.)
Still, figure that should the Allied Drive on Mainland China be successful, occupying Korea would be just as heavy hitting in terms of bombings as Okinawa. I would imagine that with Allied forces in Korea and the use of nuclear weapons against Japan, they would still surrender. Without the Bomb, however, they would probably keep fighting for quite some time.
That said, nothing about Plan Yellow would shake up either the USA getting bases close to Japan, nor the Manhattan Project. The War might very well end on schedule.