If all the Powerstore files are stored in the garage folder then you should not have to change the path and the you should try putting back to how it was which is:
<?php
// WebAssist iRite: Rich Text Editor for Dreamweaver
$WARichTextEditor_3 = CreateRichTextEditor ("ProductCartDesc", "../WA_iRite/", "750px", "200px", "Custom", "../custom/Products_Insert_ProductCartDesc1.js", "".(ValidatedField("ProductsInsert","ProductCartDesc")) ."");
?>
And make sure the you have uploaded your WA_iRite and folder to your server and that the WA_iRite folder is inside your garage folder.