How do I replace the drive cable on my Weedeater Featherlite Plus Curved shaft Trimmer?

I bought a plastic & Metal blade head for it to cut heavy brush and I think it was too heavy for my Featherlite trimmer. The drive cable snapped or disconnected inside the head or motor after about 15 minutes of trimming brush.The engine runs, but the head doesn't spin.

Can you tell me how to remove the old drive cable and install a new one?

this will probably be more expensive than the value of the unit. Be sure to consider cost vs value.