SSO through Facebook authentication

I am looking for Single-Sign-On (SSO) for our community, in order to be able to have our members easily access other portals, we want to migrate their credentials from email to an SSO that authenticates them via their Facebook profiles. This migration will give us the flexibility of adding a new tool for our members without them having to manage a separate set of logins.

Do you offer a full-service to develop and help us with this migration?. We need to ensure a seamless transition for our members. And how much you charge for this service?