The worst thing when working on your brakes, is not having the right tool. When changing brake lines or hoses, the proper wrench will save you a ton of time and frustration. Special line wrenches are designed to put the most amount of force to the fitting without slipping off. Anyone who has tried to remove a rusty brake line with a regular wrench knows that the wrench slips off way too easy and rounds off the fitting.
Here is a picture of a line wrench...
I usually advise people to buy cheaper tools if they are just a shade tree mechanic, but in this case, buy the best. Cheap line wrenches do not work, and will bend or round off the fitting before cracking it loose. Buy a snap-on, MAC or Craftsman set and good luck.
Kevin
P.S. Remember to use plenty of penetrating lubricant on the fittings before you try to remove the fitting. I use PB Blaster, or Kroil.