You will need to rebuild or replace the wheel cylinders anyway, so you can remove the brake lines now. If you don't already have a flare nut wrench, now is the time to buy a set. They look like a 6 point box end with a small section removed so that it will go over the tubing. They fit on 5 of the 6 sides of the nut so they aren't as prone to stripping. Once the brake line is off, you can get to the other bolt.
Here is a pic of the flare nut wrenches - they are worth their weight in gold (or diesel at the current rates) if you work on brass fittings much.
http://www.harborfreight.com/5-piece...set-99992.html