I'm guessing here, having not got my A-Class yet to have a look at the system, but, as a former IT guy....
Its very unlikely to be possible without serious modification. The system would need to have the correct software to play the movie formats, which I doubt it would have. Not knowing how the software for the system is stored I don't know how easy it would be to hack the system and install custom gizmos... but like any modern technology it can probably be done, if the garage can update it, it can be hacked...
All you need to do is find the right person to 'jailbreak' your A-Class, someone who has an understanding of the coding behind the software.