That's called "cutting to the chase," and to a point you're right.
The North Koreans have an agenda of their own, and OBL's hard cash is certainly attractive to them -- especially since the terrorists also further NK's aims.
Where China comes in is if we do something to slap the North Koreans down, within the borders of North Korea.
I think we can probably avoid that difficulty by simply wiping out the North Koreans when and where we find them aiding terrorists. Thus, for the camps in Kunar Province, Somalia, Sudan, or wherever we find them, pound and burn the place.
The Koreans probably cannot afford to lose too many of these advisors, and pragmatic considerations ensure that they cannot complain when we kill them. It'll end pretty quickly.