Yes, sort of.
No, Russia is not capable of projecting conventional force sufficient to occupy North Korea. Not least because the PRC is mostly in the way, and has firm ideas about that sort of thing not being allowed.
The thing is, once the DPRK actually uses nukes, everybody else takes the gloves off, because starting an intervention in any way that doesn't include an overhwhelming air attack to neutralize the North Korean arsenal with maximum force leaves a very real possibility that Kim will make Vladivostok/Harbin/Tokyo/etc glow in the dark. Accordingly, the likely response if Russia decides to intervene (and let's be clear here - Russia would really rather the PRC, or even the US, deal with this particular kettle of irradiated fish) is a counterforce strike with nuclear weapons aimed at eliminating the North Korean arsenal and ability to construct more devices for it.
The obvious arm of the military to use would be the Strategic Rocket Forces, which will resolve the problem (along with an appallingly-large fraction of the population of North Korea) in about 45 minutes from receiving the launch order, assuming that targeting has been done in advance. Caveat is that a lot of people get kind of concerned when they see any missiles leaving their silos, and you really don't want the USA or PRC misreading your intent and going all I-am-become-death-destroyer-of-worlds on your ass by mistake.
The Russian Pacific Fleet has three (or four?) SSBNs, any one of which could do the same in half the time, assuming it's on patrol. It also has 3 (well, actually 5, but two are in refit) SSGNs each of which can carry 2 dozen cruise missiles that could be nuclear-tipped land-attack variants, though in general they are armed with conventional antishipping ones, so it would need some time for the boats to return to port and be loaded for the nuclear strike role.
There are somewhere between one and two dozen Long-Range Aviation Tu-160 White Swans - aka Blackjacks to Cold-War era Westerners - at Engels on the Volga, which is on the wrong side of Russia but they have the range to get there anyway. LRA can put a couple of aircraft within standoff cruise missile range within half a day or so, with that number increasing over a few days as readiness levels are sorted out.
For Naval Aviation, the 568th Independent Composite Air Regiment at Mongokhto (which is part of the Pacific Fleet, not Long-Range Aviation like the Tu-160s) used to have 2 Tu-22M3 Backfire squadrons nominally capable of supersonic nuclear strike missions, though because they were attached to the Navy and not LRA I'm not sure they actually had nuclear weapons readily available. They'd have the same sort of readiness (for conventional strike missions) as the Blackjacks, but with a question mark over their nuclear posture. Having said that, apparently they have been transferred to the Air Force (now Aerospace Force) and have may have moved. Tu-22s have less range than Tu-160s and are supposed to not be capable of A2A refuelling (a historical treaty limitation), though there have been rumours about secret plans and clever tricks in that area if you want to include it in a story.