For smarty go to :
http://smarty.php.net/
Will really help you understand the way that xcart templates work.
For PHP try:
www.php.net
http://www.phpbuilder.com/ or
http://www.phpwizard.net/
Other than that most of the forum memebrs have made their own mods so posting a part attempted code will get a number of keen users from around the world eager to help. If that doesn't work then there are numerous of us that can do custom mods for you.
Have fun.