[CentOS] rhel3 < centos3 updates

Hi all,

I've been approached by someone who has an installation of rhel ES 3
(taroon update 2) to see whether I can take over doing security and
other updates for them (no current rhn subscription).

What I want to know is, with a suitable yum setup can I use a centos3
repository to apply updates to this box? If so, should I source updates
from centos 3.5? Does the whole box need to become a centos3 box to do this?

They'd really like to disturb the existing box (I agree) as little as
possible since it's a stable production server, and mainly just want
important security related updates etc. done.

Ok,
tia for any answers,
Stephen.
--
Stephen M. Gava <smig at users.sourceforge.net>