Happy to help. If your car is clean and virtually rust free, it will not be a terrible job.
I believe there is a new material that has copper or bronze alloyed in the steel, and these lines are reported to last longer that the old all steel model. Just keep your fittings and be prepared to do the flair or bubble flair or whatever is appropriate at your joint. You can buy the lines with the ends attached, and in that case you can use the second referenced thread as a guide.
Your lines are long, almost straight sections, and will not be hard to hand fabricate.
If the line with a leak is good everywhere but the leaking section, you may be able to "graft-in" a section of line, if you have the flare tool and some time and the unions. If you screw it up, you can go back to the original plan of replacing the whole line.
Not trying to talk you out of the ShoNut lines, simply pointing out yours are the easiest lines to fabricate.
The beauty of the ShoNut kit is you get the tortured short lines around the ABS unit that would require a professional bending tool to make the short bends, and they seem almost impossible to hand fabricate.
I ran into brake problems when the whole line system was changed and the inserts that the line screws-into backed out of the master cylinder when we unscrewed it. The thing looked like a factory installed helicoil that no one told me about. So it is crazy things that trip you up on these jobs.