This document should help on the PostgreSQL setup side: "Installation and configuration of PostgreSQL & ODBC on Redhat Linux"
http://gborg.postgresql.org/project/psqlodbc/genpage.php?howto-redhatIt even talks about how to setup PG so LOBs work from odbc.
I know I've done this in the past, when porting an MS Access app to PostgreSQL, but can't remember all the steps.
-Roberto