You will need to use the PROPLUS.msi file on the office CD to do the install. Go here http://support.microsoft.com/default...b;en-us;283686
to learn all of the switches to make an unatended install. As for the SP3 you will need the full Network version (this is ususally a large file) and run the exe. It extracts to one location before asking you for permission to procede. Copy all of the extracted files and cancel the operation. There is an msi file there.
NOTE: at the top of the link that I gave you there is a link to the Office 2000 switches.