Installing from Media is not new, but Windows Server 2008 does have a new way to create the "seed" media using a new ntdsutil ifm command. For a technet topic that explains the steps to create the media, see Installing AD DS from Media.
You can see in the topic that IFM does not help to pre-seed SYSVOL. This will be fixed in Windows Server 2008 R2. In the meantime, you can try the steps KB article 311078 to pre-seed SYSVOL.
Searching around the net, I came across these other links you might try:
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