You can see the Raw Traffic Processed under Reports -> Executive Summary and apply some filters like Date. More detailed reports with breakdown by protocol, URL, is expected to be available on a future release.
As for SNMP you can get the MIBs from the SWG GUI under Administration -> Configuratiion -> SNMP. You have the help option on that page for more information and also the Implementation Guide that includes a section called "About monitoring Symantec Web Gateway using SNMP".
HTH,
Federico