Totally new to Linux (Fedora Core 2) & PostgreSQL (7.4.2), switching from MS SQL-Server 2000!

Question - I cannot connect to my PostgreSQL, even as root account - I get login failures in both Webmin , psql and phpPgAdmin. I only want to be able to initially attach locally (until I get a handle on how to configure the environment)......What am I doing wrong ???

pg_hba.conf settings are:
local all all trust
host all all password
hostssl all all password
hostnossl all all password

PostgreSQL.conf settings are:
tcpip_socket = true
port = 5432
....everything else in this file is commented out with the #

config.inc.php settings are:
// Hostname or IP address for server. Use '' for UNIX domain socket.
$conf['servers'][0]['host'] = '';

// Database port on server (5432 is the PostgreSQL default)
$conf['servers'][0]['port'] = 5432;

$conf['extra_login_security'] = true;

1.Where are the PostgreSQL fiiles located (to set PGDATA)??
2.How do I change the password as (I think) is required????