net-SNMP configuration on CentOS4 machine for a working MRTGreporting system

Yesterday I managed to get MRTG running on a ubuntu machine generating
a beautiful page of reports of the stats on our LAN's 3 routers.
Those routers were all running the latest beta version of dd-wrt (w/
VPN support), so enabling SNMP polling on them was as easy as enabling
SNMP, putting in a Location, Contact, and Name, and then specifying
the groupnames for RO and RW access.

My boss was pleased and assigned me the task of adding our VoIP
server's stats to the report page I created. So I've snagged all of
the appropriate snmp packages and installed them to the new machine
(CentOS4); however looking at the config file has led me on a wild
goose chase for MIB/OID definitions, and although I think I've found
what I'm looking for there, I'm still at a loss.

All that I want to do in the configuration is enable 'public' to poll
a few stats on eth0 and eth0, mainly anything that would have to do
with transmission errors, in order to try to diagnose properly where
our VoIP system is dropping packets. Is there anybody that could
point me to a better source of documentation? I've found the
snmpd.conf file to be horribly obtuse about how it explains the user/
group/alias definitions. I'm still researching more documentation but
I've been going at this for awhile now and I could really use some
helpful tips or better documentation sources.

Thanks in advance!

Damon Getsman
Linux/Solaris Systems Administrator