I used to follow this pretty closely, and from what I understand there are literally thousands of prepared artillery positions in tunnels positioned to shell Seoul. The South Koreans know of thousands, and there are doubtless more, so a gun can be moved to one position, fire off a mission, then retreat to pop out somewhere else. We literally don't have enough precision munitions or bunker busters to take them all out, nor do the South Koreans. They'd mostly be firing at maximum range though, with smaller warheads and not much chance of hitting a particular area. There are missile defense systems there, used to be HAWKs (I think they are now Patriots) to take out cruise or ballistic missiles, so those likely wouldn't be much problem. There are also MLRS systems and cargo shell artillery with ICM rounds that would make any conventional assault extremely bloody for North Korea, and of course they would be meeting the forces most feared by the North Vietnamese. The North Koreans are numerous, but the South Koreans are good. Quantity does have a quality of its own, but a serious assault by North Korea would leave it effectively disarmed.
I think Obama has done pretty well during this crisis. I also don't think Red China would allow a war because of the loss of face, as North Korea is still widely seen as their vassal state. I'm guessing that the situation will return to what it was a decade ago, with North Korea aggressing by the odd kidnapping or small raid plus some sub and torpedo boat attacks and probably not much else.