(SaltStack) ID dog in SLS dog is not a dictionary

It should probably look like this:

dog:
  file.replace:    # <--------this line was your problem.
    - name: /etc/modules
    - pattern: 'bcm2708_wdog'
    - append_if_not_found: True

Lines beginning with "-" denote items in a list. In your version, you've defined the top-level "dog" element as a list containing a dictionary. Salt expects it to be a straight dictionary instead, hence the error.