What Happens If North Korea Collapses?

The piece in question talks about some plan that the US had put forth in the event that the regime in North Korea suddenly collapses. South Korea has apparently rejected the plan, for no reason that makes sense to me. The US plan had US troops entering North Korea, with the US commanders being in charge of the operation. South Korea wants to be the one in charge, since they feel that the peninsula of Korea is (or should be) one country.
What is left out here is any mention of what China would do if North Korea suddenly collapsed. I'm of the opinion that since history repeats itself, and the Chinese already entered North Korea the last time it collapsed (1950), why should things be different this time?
Our government has the idea that the South Koreans won't be able to unify the peninsula, but the threat of the entry of China into the area is a far greater problem.
War with Red China is inevitable, in my humble opinion. The leadership there is just nuts enough to let a situation like North Korea's collapse be the spark to the fire of war. The other opportunity would be a confrontation over Taiwan.
Hope I'm wrong, sort of.

I'll be back

CC