Dumb post is dumb.
ROK will tear apart the north within a few weeks at the worst. I would say within one week.
East Asians countries have proven to be relatively adaptable as far as nation-building techniques. Read: Japan, Philippines, S. Korea.
If the South decided to invest in North Korea's recovery or incorporation, it would likely be quickly repaid, as North Korea's people seem to be more than willing to give up the horrendous living conditions currently in place. Failing that, Asians have proven time and time again to be willing to exploit their neighbors without conscious.
The South has done nothing through various infringements by the North because the South is very comfortable currently, and because we (the United States) urge them to remain calm. The South has one of the highest standards of living in the world, and do not need the North one little bit, so to ignore a few deaths here and there is worth it to maintain status quo. However at some point they will snap and the North will be reincorporated, and it will likely be without much consequence assuming China remains neutral.