Eric seems completely unconcerned about reprogramming the Lunar yacht and transfers the ownership easily. It is not explained in the show why he is so capable of doing this. In a previous episode, he also seems to fully understand how "Amos"'s passport works and what its limitations are. Is it explained in the books how he is so easily able to hack security systems?
Most of the background to Erich is in the novella 'The Churn'. It isn't explicit about how and where Erich learned his skills, but is clear that his initial role in the Baltimore gangs was in creating fake IDs, with a heavy implication of IT literacy.
Erich’s stomach knotted. His bad hand closed in a tiny fist. He saw the hardness in Burton’s eyes, and it reminded him that even with his knowledge, even with his skills, there were others who could fake identity records. Others who could fake DNA profiles. Others who could do for Burton what he did.
In a locked room at its center, Erich’s custom deck was set up and primed, connected to the network and prepared to create a new identity from birth records to DNA matching to backdated newsfeed activity for the client, as soon as she arrived.