Raise the rear of the truck off the ground / floor.. Remove the wheels per the owners manual. Remove the 3 silver spring washers from the wheel studs.. Remove the brake drum. If it is rusted on, gently tap the outside corner of the drum with a hammer to break the rust free and work it off the axle.
Loosen the emergency brake cables from under the truck which will allow the shoes to collapse when you remove the adjustment wheel.
Looking at the brakes, (you can draw the placement of the springs and shoes on a piece of paper first), begin by removing the tension spring from both shoes. There are tools out there that look like large handles plyers with a hook and claw on one end that makes the job easy..
Remove the retainers that hold the shoes to the backing plate and then remove the emergency brake lever and arm.
Replace the shoes in the reverse order.. Be sure to put the long face shoe to the rear (refer to your drawing).. The shoes must now be adjusted. Expand the adjuster prior to putting the drum back. Slide the drum on and off adjusting the shoes to a slight drag on the drum when rotated.. I prefer them as snug as possible as long as you can get the drum on..
An option is to punch the access hole plug out from the backing plate (it's stamped to look like an elongated hole) to adjust the shoes from the outside. The star wheel on the adjuster moves it in or out to push the shoes in or out.. Turn the wheel until you recogize which way the star works.
After working on both sides and bolting everything back on, re-tighten the emergency brake. Test it from inside the cab with your foot.. It should not be so tight that it locks up the rear wheels when released.. However, it should not be so loose as to be pushed all the way to the floor to hold the vehicle..
Always remember.. Saftey first.. Brakes are important and if you are not comfortable with doing the job,, pay a pro...