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...