Easily set user preferences

using Mediawiki 1.12.0 is there a way to modify the default user 
preferences for existing users?
I really don't want to sign on as each user and change them. In 
particular i want to set the searched namespaces (inluding custom ones) 
and disabling FCKeditor (uncheck the use "richtext editor" in the Misc tab).

Thanks,
Matt