In 7-mode DOT you can access the "/etc" file directory by creating a share/export to it using CIFS/NFS.
The actual path is /vol/vol0/etc. If you have CIFS enabled on your Filer, an "ETC$" share is created just for that purpose by default. Good practice is to remove that share or ensure it is only accessible by local Filer administrators.
Obviously be careful what you do in there - you can cause trouble. Of course, you should be regularly snapshotting vol0 for that reason anyway, right?
Even if you don't have one of those protocols you can designate a "management station" which is allowed to access the Filer using CIFS or NFS (management station being a specific Windows or *nix server) so that you can perform certain maintenance tasks easily.
And if all else fails, there are certain diagnostic level commands that allow you direct access to the file system at the command prompt. I strongly recommend you don't go that route however.