1) change the hidden element to a text element and you can see what it outputs:
<input type="text" name="desc" id="desc" value="<?php echo $eCart1->TotalColumn("FullDetails") ?>" />
2) World pay offers 5 custom variables by default M_CustomVar1 - 6, these are usually used for passing shipping information
you can create your own custom variable using whatever name you like, but prefacing it with MC_ or CM_:
<input type="hidden" name="MC_LongDescription" id="MC_LongDescription" value="" />
you would not use a post value for the long description, but a cart value.
3) add a cart repeat region to the page by going to the server behaviors panel, clicking the plus button and selecting eCart -> Cart Display -> Repeat Cart region.
