You should be brave here and begin by reading Marx for yourself. He has a reputation for being difficult but the Communist Manifesto is probably his (and Engels) most accessible work. This is just a short relevant extract. Only when you have read this should you turn to Spalding. His article examines the significance of the Communist Manifesto.

The second extract you need to read is much shorter and comes from his famous preface of 1859. This contains all the essential ideas on history and revolution. You need to read it a few times and then try to produce a summary diagram that explains Marx's theory of history and revolution. 

Mr Jones-Nerzic's animated summary diagram of Marx's theory of history.

Video - The Spectre of Marxism: Karl Marx (Two Programmes) Available from the library.

The Library has lots of introductory books on Marxism (335.4). The best is Alex Callinicos The Revolutionary Ideas of Karl Marx (335.43), best because Callinicos is a Marxist. His new 1995 introduction explains why he thinks the ideas of Marx are still relevant. In complete contrast is the recent excellent biography of Marx by my favourite newspaper columnist Francis Wheen (335.412), he really brings Marx alive. 

Marx dies in 1883. Before the First World War we can already identify a division between those who would later be known as Social Democrats and those who will become Communists. The 1899 text by Eduard Bernstein Evolutionary Socialism (Spalding 39-40) important to the history of this division. Lenin's leadership of Bolshevik faction of the Russian Social Democrats in 1903 is important for a different reason. (Spalding 51-2)

It is certainly worth reading the whole of the chapter but focus your notemaking on Germany (37-41) and Russia and Lenin (49-52). 

The Conclusion (53-5) is also worth noting.