I have my main site at location 1 where my CIC is with a full CIC backup at location 2. Now I want to install location 3 so that location connect to Location 1 for CIC capabilities. Then if my WAN between location 1 and 3 failed, I want my people at location 3 to be able to do inbound/outbound and intercom. My first thought was to only put a SIP proxy to that location for survivability purposes but do I also need a media server over there or the SIP proxy can be auto sufficient? Thank you for your help,

Just for call routing, all you need is the SIP Proxy (configured as a Managed SIP Proxy in Interaction Administrator). Media Server is recommended if you have calls going directly into that remote location via a local gateway or SIP trunk and you want to record them. (I presume you have a local gateway there, since if the WAN goes down there's no other way for the calls to get into the remote location...)