One reason automakers favor a front-disc/rear-drum configuration (aside from the low cost), is that drum brakes require a simpler -- and cheaper -- mechanism to operate the parking brake. On drum brakes, the parking brake cable controls a lever that's connected to the brake shoes. With disc brakes, the lever attaches to a separate mechanical device inside the caliper piston that pushes the piston into the pads. On some cars, the lever attaches to a separate drum inside the rear brake rotor, depending on single-piston or four-piston calipers brakes.
What this means for your conversion is that, depending on your vehicle, you may need to install an entirely new parking brake system. If you're lucky and your new brakes are compatible with your parking brake system, all you'll need to do is disconnect the parking brake before removing the old brakes, and then reconnect it after you've installed the new ones.
Removing The Drum Brakes
Rear drum removal is essentially the same as removing front drums, except for that pesky parking brake. Start by removing the wheels and then the dust cap, the center nut and washer and the brake-drum bolts. Before you remove the drum, you need to disconnect the brake hose and parking brake cable. After you remove the drum, inspect the spindle and either replace it or reuse it. Then reposition and secure the steering arm.
Installing The Disc Brakes
Attach the rotor to the spindle, followed by the washer, the bearing and nut and the cotter pin. Then put the dust cap on and move on to the caliper assembly.
Before positioning the caliper on the rotor, attach the new brake lines and install the pads. Then place the caliper over the rotor and attach the parking brake and the brake lines. Put the wheels and tires back on and you're nearly done.
As with the front conversion, it's extremely important to bleed the brakes and refresh the brake fluid. Equally important is testing the parking brake and making necessary adjustments.