Jamie, playing a little devil's advocate here, but following through with the story, you were well aware of the timeline from the very beginning, were also involved in selecting of Justin, and was responsible for tuning a vehicle that should have been in proper working condition and "ready to be tuned" when you got it, but it is VERY clear it was nowhere near that condition.
1) Why did you bother to attempt to tune the vehicle without confirming for yourself the vehicle was in proper working condition and
2) If you knew it was already in knackered condition, why take full payment and not return a proper product?? Payment was made to MARSH TUNING, so that in itself holds you liable for a percentage of this ordeal. The company itself bears your name.
It makes it tough to separate yourself from the situation when you were well aware of all the details, timelines and who was to receive payment and what was to be presented to the customer..............