As I imagine you have seen, CL_CRM_DOCUMENTS is a superior layer that ends calling the functions on your link, I wouldn't waste my time on that. If you have superior layers take advantage of that.
A good starting point is attach a document in web ui while you have break points in the methods that you are interest like CREATE_WITH_TABLE (for example) once the debugger stops F7 to the upper layer and try to understand what's happening.
Thats the way how I did it in the past 
I should write a document 