I think samba-common is required for samba and is installed when samba is.

You must have changed something, samba doesn't change its configuration by itself. Maybe you should post your smb.conf again if its different from the one you already posted. Perhaps a forgotten samba service restart.

I found SWAT a good tool to use when I was first using samba, because it shows basic options and links to the help file that explains the various options.