Look closely for that one spline that’s different on the box and coupler. It can only go on one way. You’ll probably need a puller to take off the pitman arm.
There should be a nut on the pivot ball on the frame rail bracket that holds the pivot ball in the Z bar. Loosen it up and pivot the Z bar up and slide it out of the other end.
Replace the whole frame rail. When I did mine. I had the car on jack stands and made a brace from the floor to the rear bumper frame rail that way after you take out the old frame rail it will go in exactly where it came out. Front pretty much goes the same way. A lot easier if you have to...
Sounds like you got wires crossed somewhere or burned through together. You must have voltage to the coil when the car is off if it keeps running and the coil gets hot
I just did mine , I prepped and painted it like everything else. I’m not sure what it’s made of. I sanded it by hand so I wouldn’t go through it. The black on the quarter panel looks like someone just coated the rust with something. Or just put black silicone to seal the mounting hole