Ug, confused 2 different threads. :p I'm dealing with 2 threads where you and someone else are trying to edit files that shouldn't be edited. 99% of the time when someone wants to edit a file its because they aren't using the GUI and manual properly.
I'm not sure what you are trying to do. If it can't join the AD, and you are trying to create some accounts, the GUI allows you to do that. That's about the best option I can give as you really have provided no information on what you are trying to edit in smb.conf or why.
In short, I'd be willing to bet whatever you are trying to do can be done from the GUI. But leading to editing configuration files isn't going to work out for you in the long term. There's an overwhelming body of evidence that its just not a very smart thing to do.