well, theres some classic questions you can throw into your answers, which lets you take control a little bit.
lenin vs. trotsky: what was the nature of their split?
communism in one country vs internationalism. what was in the soviet unions best interest? in int'l communism's best interest?
was the soviet union / communist bloc ever an autonomous, parallel 'world system' to capitalism, or was it just a deformed space within it? (try to avoid referenceing marx here!)
sino-soviet split. why?
what caused the fall of communism? global capitalism, or some kind of inherent flaw in so-called 'communism'?
good luck, its a very interesting subject.