This reply is very late for your needs, but it may help someone else with the same problem.
1. Yes, all of the hard brake lines are available, and are pretty inexpensive.
2. They are each pretty easy to replace, if you have the proper tools and the nerve to work on your own brake lines. If you don't have brake line wrenches, get some. All of the fittings are the same size, so you only need two wrenches.
3. I replaced all of the hard lines, and the flexible lines, on my 2000 Xterra. The only line that was difficult was the line that went along the frame rail from the front to the back of the truck.
4. The plastic clips that hold the brake lines in place along the fire wall in the front and along the frame to the back will probably break when you snap out the old lines. Get some replacements, they are also cheap.
5. Purchase the replacement brake lines from your local dealer, shipping for brake lines is very expensive, so let the dealer cover those costs.
6. If you live in the rust belt, the metal brake line hold downs on the rear axle will break off when you try and bend them to remove the brake line. Just use zip ties to hold the brake line in place.
7. Be very careful when threading in the new brake lines to the junction points. Do not cross thread these connections!
If you don't feel comfortable working on the brake lines, have a mechanic do this for you.
Good luck with your project