The Chicago Manual of Style is the authoritative source on the publishing process, style and usage, and the ‘scholarly apparatus’ such as bibliographies. The 16th edition was published in 2010. This guide incorporates some of its advice.
The Editorial Freelancers Association, a professional organization, maintains a searchable online directory of its members.
The directory allows you to search for editors with particular skills, subject specialties, software capabilities, and geographic locations. Look for the Find a Freelancer link on the EFA main page.