There are many sub sections to the essay you have been asked to write, so our first educator answer had better deal with your first theme - the idea of man versus nature and the conflict issues around that (particularly in the light of Rousseau's belief that man's natural state was best as that state brought mankind freedom from social convention.)
At the start of the novel the Virginian is a 'rough diamond.' In essence he is 'good' but there is a certain wildness about him, the vestiges perhaps of his original 'animal' nature. This unconventional personality will conflict with his local societal conventions so cite examples of this contrast where you can.
Hungry for a successful lifestyle and keen to win his ladylike sweetheart (who represents man's elevation above nature and natural animal limitations) the Virginian experiences conflict in pitting himself against taxing projects and the local unforgiving landscape of the natural world. He wins through however and impresses his ranch owning boss, proving his leadership skills as he guides man and beast eastwards to trade the cattle. This task too presents conflict as the Virginian has to deal with cattle rustlers, another epic 'test' he passes admirably on his way upwards to transcend his basic nature. Ironically, we see this character develop beyond the natural 'animal' state as he becomes a thinking, discerning reader of Shakespeare and a fan of other cultural pursuits under Molly's refined influence. It seems to be her presence that acts as the catalyst for the Virginian's resolution of the conflict within himself - overcoming his wildness and natural drives to begin the journey towards nobility.