you can install bonus stuff and custom stuff after you install throne of bhall. i have heard that it messes up if you install tob after you add custom stuff.
something about changing the "last modified date" of the dialog.tlk file. but if you already have tob installed it should be ok. besides, its just a couple of files added to your overide folder. you could always delete them if it messes it up.
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Get The IronWorks Winamp skin
Slackerboys Custom Characters