When Vincente Bravo meets "El Lider" (Spanish for The Leader), they mention the last time they were together ten years ago in the sugar cane fields. The country is not mentioned, but it is strongly implied that it was during the Cuban Revolution when Fidel Castro took power.
Barney's latest contraption, is what we call in modern parlance as a Remotely Operated Vehicle (ROV) , with drill, is quite similar to Pipeline Inspection Gauge or PIG used by the Oil & Gas Industry to examine the structural integrity of pipelines internally.
Steganography is the practice of concealing messages or information in plain and open view, or within another message (non-secret information). In the case of this installment, Jim said the code is hidden by a photographic overlay and a chemical spray is placed between the code and photo.
The revolutionary that Paris impersonates is loosely based on Ernesto 'Che' Guevara, the Argentine Marxist revolutionary.