ashis,
"I" thought learning SME 7.X was going to be easy. There are features (as all who read the forums know) which should work right out of the box. Knowing absolutely nothing about Linux I dove in head first.
Webserver, Email, FTP, Spam & Virus Checking, File Sharing, Domain Controller for Windows Domains - with simple administration. The distro worked flawlessly out of the box until I wanted to add something or change settings. This is where it gets a little hairy.
The best way is to have a test box with SME on it and simply play with it. When it breaks check the forums to see if someone else has found the fix. If not your only a reload away from a running server again.
Document what your trying to do and the steps you took. Some day this will be invaluable to others! Most of all don't give up. Once you've written your first template and it works the magic all makes sense. The guys who develop this distro are the most knowledgeable you'll ever find! And their not afraid to help - in breaking things it helps them to discover new ways to make it unbreakable.
It's not easy - read the documentation at least three times! About the third time it all starts to make sense. Try installing something you find useful in the contribs and see if it works correctly. SME server is free for us to use but it's like everything else that's free - your going to have to spend time and energy at your expense to learn how it works by reading, experiencing and sharing with others.
Good luck,
Paul