Adding template to garland, preprocess page doesn't work
If processfront is an alias for a specific node, let's say 228, then its system path is really node/228 and arg(0) will be node.  If you've set your system up so that this node is your front page, you can just use page-front.tpl.php and drupal will take care of it automagically.  Otherwise, you can use drupal_get_path_alias() and check against that.