Ispconfig has no default site, so you can use any domain name for sites in ispconfig. The reason why you should not use your main domain as hostname is postfix. So you use something like server1.example.com and not example.com as hostname as it is described in the install guide.
You dont have to buy any guides to install ispconfig, all install guides are freely available here at howtoforge. And to add a website you dont need a guide, just click on new website, enter the domain name and click sve. Thats all and described many times here in he forum.
Last edited by till; 2nd April 2012 at 23:24.