where can you buy all the brake linesthat run along the back axle? And once I have them how would you go about replacing them. The one that is there is rusted out so I need to replace everything from where the line comes back from the master cylinder Thanks

Find someone in your area who knows what they are doing to help/teach you, or take to a shop and have it repaired. You don't want your 2nd to last mistake cause your last accident.