I don't klnow where the N KOreans got the helos, but they probably got old, commercial ones (they started making the intital OH-6's in 1963) from some foreign user that was unloading them, and then converted them to military use. The ones they have are most likely not up to S> Korean standards.
In the gunship variety, here's a pic of the later MD530MG Defender and another of the MD530F variant (they were made in the 1980's):
Beyond that, everything you say about the vast quantities of N Korean ordinance pointed south is true and it is a very dicey situation. N Koreans are hungry and there's lost to eat just south of the border. My own personal opinion is that N Korea always has been and still is a puppet on a string for the ChiComms. All of the talk otherwise by both parties, IMHO, is just an extension of Sun Ztu's philosophy that all warfare is deception. But tha's just my opinion.
That said, I'm not overly concerned about their conventional forces.
They are just a saber to rattle in the face of South Korea, and in the tradition of Sun Ztu, one never rattles a weapon that will actually be used.
But nukes are a whole different situation.