Dave - NAPA for the correct line size, if you are lucky they may have stainless if not standard will do for the next 10 years or so. Make sure you get the fittings for the line ends. What worked for me was to disconnect the front line where it connects to the brake block on the frame, left wheel house just behind the inner plastic fender and then disconnect where it connects to the load sensing device aft of the fuel tank. Take the old piece out in one section - now leaving about 4" run wild at whatever end you decide to start - take the spool of new line (sorry forgot to mention its probably 25") and wire tie a section to the old, using a tube bender make your first bend copying the old line. Wire tie before and after the first bend and keep repeating until to get to the last bend. You'll be best sitting in the driveway or if there's enough room somewhere out of the sun you'll need about as much space as it would take to park your truck to work. My neighbors got a good laugh at me fighting two skinny snakes in my driveway back 5 years or so when I had to do mine. Anyway, once you get the new line bent up where it matches the old cut the ends - leave about 1/2" extra tube on each end for fudge factor when it comes to making up the double flares - Ah - don't forget to install the line nuts before making the double flares - bet you can guess how I'm able to offer that little reminder . . .
Oh, the old line will fish out from the front, feeding it thru the space between the engine and the front differential (if 4WD) not sure on 2WD. Then the new line will feed the opposite way. Install using the clips so it doesn't contact the frame, if it contacts the frame you can wire tie a piece of hose to prevent chafing down the road. Once the line is in the body hand thread both nuts in all the way then back out the rear nut a few turns - tighten the front one securely. Pour in the brake fluid and it should gravity flow out the rear nut you left loose - if not there's a little block under the m-cylinder (rear only abs assuming your 99 is like mine) with a rubber cap covering a little valve pop-up thing (forget what its called) have someone step on the pedal and catch the pop-up and secure it from going back into the block - a set of needle nose vice-grips with electrical tape on the tips works well so as not to mar the valve pop-up thing.
This should allow gravity flow. If not go the old fashion route you at the rear nut, someone else at the pedal (unless you have a power bleed kit) until you get fluid at the rear nut - tighten securely. Then proceed to the right rear and etc.
If you don't have a hard pedal you may have to disconnect the load sensing arm rod to the frame and place arm in the up or fully down position to get good flow/all the air out of the sensing device.
It's fun, but beats the heck out of paying someone else to do it.
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