MY NEIGHBOR DROVE MY 300 TO THE STORE AND BACK AND IT'S NEVER RUN AGAIN. THE MECHANIC TOLD ME THE ENGINE WAS OVERHEATED AND SHE'S DEAD. WHAT HAPPENS WHEN A DEISEL GETS TOO HOT? IS THE HEAD SHOT OR PISTONS? IS WORTH REBUILDING OR SHOULD I GET ANOTHER MOTOR? HOW ABOUT A LATER TURBO?