Once you get it running again, make SURE you check your hydroboost. As said, it sounds like the nitrogen cannister burst and forced fluid out of the system. The service manual has the procedure, but an easy way to test it is to find a large parking lot, slowly drive the truck, shut off the engine, and apply the brakes. The nitrogen cannister is intended to give you 3 good brake assists or more. If the brake pedal is hard right away with no assist, the hyrdroboost is shot. You'll only know this if you need brakes in an emergency such as running out of fuel, but trust me you don't want to try to stop this truck without hydroboost. If you just fix the bubbles in the fluid everything will seem normal until you need it. Did I mention to make SURE you check it if you've had a P/S problem?