Replacing just the rear section of the line is doable Jack, as long as you do the proper flares and joining them with a union. Compression fittings are not acceptable for brake lines. The tough part is the sharp bend in the line, just above where it screws into the rear flex hose. Not much room there, and its hard to reach. Sometimes, you can take the U clip off the brake hose, pull the hose down below the frame crossmember, poke the steel line through that hole where the hose goes through, and start threading the steel line into the hose, the push the hose back up into the frame, reinstall the U clip, the snug the steel line up with an open end wrench, then use a flare nut wrench to tighten the fitting. Depending on where the new line is joined in on the frame, that should be reasonably easy to access. I installed a pre-bent line kit on my '80 Malibu, with the car on stands in my garage. That line that runs from front to rear was a pain, but I was able to get it done. I started at the rear (after making sure that I had run the line around everything else properly-it took a couple of tries), then worked my way towards the front. Patience was the key thing on that one.
