I need to decode a packet sent using TIBCO-RV and pull fields out of the header and skip over the message body. I have not been able to any examples or documentation. Does anybody know of any open source applications that might do this or if there is a Wireshark dissector out there somewhere?
Maybe you should try applying for a license and getting the official documentation. According to Wikipedia:
TIBCO provides messaging APIs in C, C++, Java, Visual BASIC , Perl and .NET to receive data feeds on MS Excel spreadsheets and other applications of choice.
Failing that, you could perhaps dive into the TIBCO:RV Perl module.