A good starting place would be here http://us2.samba.org/samba/docs/man/Samba-HOWTO-Collection/domain-member.html#ads-member and here http://us2.samba.org/samba/docs/man/Samba-Guide/DomApps.html#id2594564 But I think you need to ask yourself why you want kerberos. There's some uncertainty because you don't know whether you need the server package or the workstation package. But since you are wanting this to be a domain member of a Windows Server 2003 Active Directory domain, I don't see you needing to make the Samba server a KDC. You just want, I think, to be able to get tickets from the Windows Server 2003 KDC. And the links above should tell you everything you need to know for that. As for the software you need, you may already have enough to do the above. Do a rpm -qa | grep krb5 and post the results.
