Problems with Installation of Perl-DBD-PG

I confess, my experience with postgresql and perl is limited to
installation. I am currently running Red Hat 9 (which is a-week-old
knowledge) on the administrator seat.

SPECS:
Red Hat 9
Postgresql 7.3.3
Perl 5.8.0

The Postgresql was a successful installation based on the Short Version
Installation commands stated in the INSTALL text. Database has been
installed and the test database has been created.

PROBLEMS:
But, when i wanted to install perl-DBD-PG-1.21...rpm, it failed and
displayed these error statements:

> warning: perl-DBD-Pg-1.21-2.i386.rpm: V3 DSA signature: NOKEY, key ID db42a60e
> error: Failed dependencies:
> libpq.so.3 is needed by perl-DBD-Pg-1.21-2

I have edited the file:
/etc/ld.so.conf

and added a line:
/usr/local/pgsql/lib

and run ldconfig as a root user (although after pressing 'Enter', no visible
confirmation the this command was successful)

Thank you.