Head gasket replacement instructions

Drove truck home from work (1 1/2 hour drive). Everything normal, no problems, no doors, no alarms, nothing wrong. Next morning, when checking fluids before leaving for work again, found reservoir starting to change state into a " light/slushy type form. Drove other car to work. Came home checked engine oil condition, no change in color, odor, or viscosity, checked transmission fluid same results, checked actual fluid in radiator, no change, no harm was done.

Drained all existing coolant from radiator, after cleaning out overflow with room temperature water, also, flushed all hoses in and out of coolant system. After allowing all to completely empty itself, I refilled with new dexcool coolant, only bumping engine at first to move fluid level so able to top off system. Then at idle only, while watching and listening to engine, allowed to idle with cab heat on until change in cab temperature from cold to just passed warm present. Then shut off engine, had to lay down before leaving for work again. Haven't actually driven this vehicle yet, still investigating what/why/how this occurred.

Respectfully request your input if possible. Thanks.