The brake lines themselves (at least in the rear) look really good, I'm going to try to reuse them.
So are you only going to replace the flex lines at the wheels?
If you look under the hood at the ABS pump you will see that there are some short lines that exit the ABS pump and go to a manifold about 12 inches toward the rear. The manifold is where you can disconnect the hard lines for removal without touching anything from the master cylinder to the manifold. Just after the manifold there are some short sections of flex hose in the hard line that are secured with pressed fittings. These reduce vibration in the hard lines and allow for easier installation and removal. These pressed fittings are one of the things that are prone to fail so you should look for signs of leakage there. The lines may have brake fluid on them below the pressed fittings or the frame right below may have an accumulation of brake fluid.
The flex hoses at the wheels are often left in place until the hard lines are changed because it is pretty difficult to undo the fitting between the hard line and flex hose without breaking the hard line. The fittings are not very hard metal so they round off easily. If you want to replace the flex lines, start spraying the fittings with PB blaster every day for about a week before you do the work. Also spray the threads of the bolt that mounts the flex hose to the frame. I generally replace these bolts.
You can use a 6" pipe wrench, a basin wrench, or vice grips to loosen the fitting. There are some specialized flare nut wrenches that may work but I find something like a pipe wrench or basin wrench to work best, especially if it rounds off. Carefully try to loosen the fittings without breaking anything. Have an oil pan ready since you will get brake fluid to flow out.
If you are going to do all 4 wheels, it's a good time to flush your brake fluid so you would start with the passengers rear wheel (the one that doesn't have the 3-way fitting and is the end of the line). Let me know if you need a procedure for that.
Not to lengthen the list but this is also a good time to do service on the calipers, dust shields, parking brakes, etc.