I've said it before, the best documentation is in the Samba website - http://samba.org/

In their learn samba menu they have an offical how-to and a by-example guide.

As I also said before, SWAT is an excellent configuration tool, why worry about a text file when a graphic utility can do much of the work for you? Do notice that I said 'much of the work', once you have Samba running you should tweak its configuration for your particular settings.