brake line size

I'm wondering what size the brake lines on a 1997 tahoe 4x4 are. I had a bad day with the Tahoe today. I bought it last Feb. with 230 000 km and now I have 252000 km. Besides oil changes I haven't done anything to the truck. Today it started to miss on the hills and then the engine light started blinking. I pulled over and turned it off, restarted it and the light went out. I'm thinking a bad plug wire. A few miles down the road I stopped and when I went to leave my brake pedal went to the floor. Broken line!! I still love my truck though. Is anyone using bosch plug wires?