Learn a small example and enter one musical phrase before attempting a full score. Compile often and keep reusable definitions for instruments or repeated notation.
Inspect the final pages for readability and page turns, since automated engraving still benefits from a musician reviewing the result. Yes. LilyPond interprets a notation language and produces engraved output. An editor such as Frescobaldi can provide previews and navigation while LilyPond performs the engraving.