I've heard that one difference, though not the only one, between North Korean and the Korean spoken by people who were born in South Korea is the vocabulary.
Is knowing vocabulary from Russian, or languages which get loanwords from Russian, useful for knowing words which occur in North Korean, but not in the Korean spoken by those who were born in South Korea?
More general question, but no mention of the role of Russian: What, if any, are the primary differences between Korean as spoken in the North and that spoken in the South?