As I mentioned and others have said, there is no substitute for studying the NR and the Learning Manual, in detail, exhaustively. It's a powerful program with enormous control, unlike typical GUI programs. It's no different to learning to play tin whistle. Nobody would expect to learn it in a week. Because lilypond is text based, you have to fully understand the syntax and semantics for advanced work. If you are keen, you can learn Scheme and program functions and extensions. The documentation is exceptionally good, given that this is open source software.
[Re the Larsen ornaments, I can't see how to integrate Scheme and Lilypond in safe mode. Possibly impossible!]