Server 2k3 SP1 Upgrade to SP2 - Possible issues that can be avoided?

Currently in our Company we have (2) Windows Server 2003 Standard Edt. SP1 machines attached to our System I (AS400) v5r4 via IXA SCSI.  Both windows servers can be moderately controlled via the 400 for basic administration such as Backup and shutdown/reboot.  One windows server runs Exchange 2003 SP2, Symantec Corporate 10.2, Routing and Remote Access and DNS and is sitting at Service Pack 1 still.  The other windows server is our DC running as the file server running a few 3rd party applications and hosts DNS and DHCP.  Both windows servers are at SP 1 and I would like to bring them to SP 2  which I believe is required to install the DNS Poison Cache hotfix?  I am asking you guys for any guidelines I will need to follow ( Services need to shutdown before the upgrade, hotfixes needed etc...) in order to make it a smooth transition with no headaches :)  Any articles or helpful tips to watch out for would be greatly appreciated.  Thanks in advance!