The biggest benefit I would see to an online course would be to get the theory down of how a 4-stroke engine works, what effect ignition timing has, and how electronics can vary fuel delivery and timing to make more power or increase fuel economy. Beyond that, the specifics to your DD and project car will come primarily from applying what you could learn through an online course (or book from the library, surfing the Internet such as "howstuffworks.com", or forums).
-Rod