Underneath its electronics, the 6.5L EFI diesel engine is a basic V8 diesel powerplant. The fuel pump, lines, and injectors still deliver fuel according to the basic rules of hydraulics. Electronics simply make them operate more precisely. Your understanding of the 6.5L mechanical systems and how they relate to each other is still indispensable for troubleshooting and repairing faults.
With the 6.5L EFI, a basic understanding of electronics is also necessary. Being able to read wiring schematics will allow you to identify components, wire colors, pin numbers, and wire routing when electrical diagnosis is required. The diagnostic trouble trees contained in Sections 3 and 10 of the Driveability and Emissions (Diesel) Service Manual are based on the schematics and require at least elementary knowledge of electrical theory.