I am rather surprised at the beliefs being stated here regarding exactly how dangerous a threat the DPRK continues to present. There are a number of issues that seem to have been either forgotten or discounted too quickly.
1. The DPRK leadership, while of questionable mental stability, is NOT stupid. It is very aware that the ROK/USFK will own the skies in short order. It is also aware that it is far on the weak side of the technology scales. That means that any attack from the North will be the international equivalent of a mugging, all all out effort to disable the target before they can react or call for assistance. The DPRK will not provide the ROK and its allies time to build up forces, even time to fully mobilize ROK reserves is very unlikely.
2. The vast majority of the DPRK's artillery assets are sited in very well designed and located bunkers, ones that take full advantage of the rough terrain for which the Korean Peninsula is justly famous. The tubes are indeed old but they are not going to be used to act as counter battery against mobile forces. They will be striking targets that have been surveyed and updates literally for decades. Many of the shelters use natural caves, meaning it is unlikely that even a 2,000 pound LGB will be able to penetrate the overhead, a number of caves are known to have multiple entrances, with the entrances often modified so there is a dogleg, sometimes with the additional protection of blast doors, meaning any strike on the entrance will potentially fail to destroy the tube. Very few of these sites will survive beyond the first 72 hours of any engagement, however, a Koksan SP 170mm piece can fire a round ever 90 seconds and move back into its protected shelter under its own power. The same is true for the numerous 240mm MLR, all of which are designed for "shoot and scoot". Such assets are notoriously difficult to track down, especially in the sort of terrain found on the Peninsula.
3. No one has even mentioned the very substantial DPRK SSM arsenal. Current estimates put the inventory around 1,000 launchers, the vast majority of them mobile (The ROK has 8 PAC-2/PAC-3 batteries). In the 1991 Gulf War, despite a concerted effort by Coalition aircraft operating with virtually no opposition, there were ZERO confirmed kills of launchers (in 42 documented sightings, many by F-15E armed with PMG, only THREE ended with ordnance actually being released, in none of these cases were positive results obtained). These launchers, while not invulnerable, are nonetheless very difficult targets, virtually invisible until firing, and able to exits an area within five minutes of launching.
Of the ~1,000 missiles, around ~700 have enough range to strike anywhere in the ROK from north of Pyongyang, with around 200 able to strike all of Honshu, Kyushu, and Shikoku from sites near the Yalu (the same missiles, the Rodong-1, is believed to have sufficient range to strike U.S. bases on Okinawa). The DPRK has effectively taken out an advertisement bragging about its possession of VX nerve agent with the assassination of Kim's brother. Keeping mind my comparison to a mugging, there is little reason to expect the DPRK to withhold the most effective (short a nuclear device) weapon in their inventory. Perhaps even more worrisome than the nerve agent, is the strong evidence that the North has large stocks of persistent agents like mustard gas that would be an immediate and catastrophic medical disaster far beyond the capacity of any country to manage.
While it is striking unlikely that the DPRK will ever attack the ROK, any such assault would devastate one of the world's largest economies.