I'm the SMS Administrator at my current position. Here are some links I found reading up on SMS 2003 with sp3.
http://www.microsoft.com/technet/prodtechnol/sms/sms2003/upgradecheck/61facc2f-b0ac-4f73-95be-e3cf776023bf.mspx?mfr=true
http://www.microsoft.com/technet/sms/2003/downloads/servicepacks/sp3.mspx
Cheers,
Steve