Hegel's relation to Marxism is that Marx and Engels were big Hegel nerds (the Young Hegelians) before they got cool and they decided to incorporate a small piece of Hegel's thinking (the dialectic) while flipping all the rest on its head.

So it's useful to know Hegel so you know the lineage of thought but important to know that Marx used Hegelian thought as a critical target more than anything.