This almost sucked. Hard.
The Microsoft Technet article I linked to previously about moving the WSS Content Database in WSS 2003 is pretty good! Except for the last section, under Moving the Datases, subsection “Set the content database in Windows SharePoint Services”.
Unfortunately, the article says you should, for each Virtual Server, remove/disconnect each content database, THEN add the new content database. This is ass-backwards, and SharePoint (SP2, at least) won’t let you do it. It will only work if you add the new content database first and THEN remove the old database.
I thought my goose was cooked until we tried that, then we were okay.
In my dream world, Microsoft and all other vendors will actually QA their documentation as thoroughly as they say the QA their code.