A: If you would like to change the appearance of the storefront visible to your customers you should do this by altering HTML templates:
http://www.XXXXXXXXXXX.com/cgi-bin/ppadmin.cgi?action=html

You can find detailed instructions on how to do this here: http://shoppingcart.org/paypalhelp/DCForumID7/6.html

You can update templates via administrative area. You do not have to do this via FTP.