Hi,
Each server name must be unique you cannot setup a trust between to DC's both called Server01.
After that you need to start with setting up name resolution between the to domain, the easiest way to do this is to use a conditional forwarder on both sides.
So on the DNS server for contoso.com you configure a Conditonal Forwarder to -> bimfirm.com and on the DNS for for the bimfirm.com you do it for contoso.com.
More information about conditional forwarders see : http://technet.microsoft.com/en-us/library/cc794735(WS.10).aspx
Regards,
jörgen