They do make a special tool for that big spring that makes it a lot easier to install and remove. Don't know if a parts store in your area may have one they rent?
J 38400 Brake Shoe Spanner and Spring Remover
Important: Pushing forward on the park brake cable will unlock the cable from the retainer allowing the cable to be removed from the park brake lever.
Important: When removing the park brake cable from the lever, the park brake return spring will remain attached to the lever. DO NOT remove the return spring from the lever. If the return spring becomes separated from the lever, replace the rear brake shoes. The lever is part of the brake shoe assembly.
Important: When installing the park brake cable into the lever, a snap or clip should be felt or heard. This will indicate that the park brake cable is properly in seated in the lever.
Important: Ensure that the retractor spring is properly seated in the retaining bracket at the bottom of the backing plate.
Important: In the following service procedure, the retractor spring can be installed by the use of either the special tool called out or by the use or a pair of channel locks.