Writing a long document can be really intimidating however it can be made a lot easier by breaking it into smaller pieces.
Your first step should be to break up your topics into groups. Each group will make between one and three paragraphs in the end. Having only to write a paragraph at a time is a lot easier than a big document.
Under each heading you should bullet point out what it is you want to say.
Each paragraph should be like a mini essay of their own. Opening sentence introducing an idea, one or two sentences for each of your bullet points, finally wrapping the paragraph up with a conclusion.
Your document should have 3 sections: Introduction, Body, and Conclusion. You should start in the body to develop your argument and then tackle the Introduction and Conclusion at the end.
Google docs has a very convenient way to manage citations within your document.
To open up the citations menu click Tools > Citations.
You can then add sources by inserting data into the form. The suggested elements to add have asterixis but you can add extra data if you have it.
When you want to insert a reference press the "Cite" button and you can also add a bibliography at the end.