Remember the Iraqi army fought two bloody war in the last 20 years and they were very limited because of the sanctions to modernise their army. The N-K army is three to four times bigger and is well equiped, because of close relations with China and Russia. And the most important factor. They have nukes.
Other considerations.
China would not allow a war in its backyard against a natural ally.
South Korea would not allow a war in which they could suffer a lot of losses.
Syria is likely. N-K and even Iran are not an option. N-K will never be an option. Iran is not a option for the moment because of the cost to conquer and occupy it. Any idea how much this cakewalk in Iraq has costed?