Tools and tips to read and understand open source?

[Mkz]

Originally Posted by 5Alive

Do you consider producing UML diagrams will be a helpful aid to my understanding of how things work together?

For this specific item, I'd recommend that you build your diagrams on paper or on your mind. If you start using UML just because it's "cool" or "popular", and it's one other thing you don't master, it will make the task even harder.
I personally find that a couple of drawings are more helpful than taking the time to learn and follow the standards of UML.