First of all, get a second opinion, especially on cost.....
There are a lot of lines that just have surface rust......and then there are lines that are so bad that if you breathe on them, they will leak....
Lines are not plug and play, in other words, you can't get lines that are bent to shape/length and you just install them....
In some instances, just a small section has to be repaired......in this case you can buy straight, pre-cut pieces with fittings.....you make your cut to fit the length you buy....can do this on a bent section, by using a string the same length as the replacement piece, and holding the string along it's length, you can determine where to make your cuts.....however you will need a fitting for each cut, and a union for each cut....where you make the cut, you will need a bubble flare tool to create a bubble flare on the old lines.......
Brake lines are easy to bend,,,,,,,I use a 2" pipe in a vise.......hold the new line next to the old one(just like a templet) to make the bends in the new line like the old one....
For real long lines, buy a long spool of brake line and cut to the length you need.......or you can just buy long sections and union them together(which is good to do with long lines with a lot of bends in them)....
Fairly easy to do, but next to impossible to do without a lift....