Need direction for OAM/OIF install

This is a new install.  All 11.1.1.7 as this project's deadline is only 2 months away.   OID, OAM currently fronting EBS 12.1.3 and OBIEE 11.1.1.7 with webgates/Accessgate.

At last minute they add a requirement to do a federated approach (OIF) to allow access from users authenticated elsewhere. 

They also want OID to be the user repository for Sharepoint authentication.

I need some direction on how to:

     1) implement OIF with OAM    (I read that OIF can front OAM or visa versa)

     2) How to deal with both sets (oid authenticated or externally authenticated) of users

          Do I have multiple URLS for each user type?

          How do I go about testing this for both user types?