for the address to the ipn page, see the power store admin panel under settings _> Payment Gateway settings.
The address will look like:
http://mydomain.com/ps_4_5/webassist/plugins/shopping_cart/ipn.php
the order info will not be stored untill paypal makes the IPN post to the IPN page.
like I said before, Paypal standard is not a real time payment gateway meaning that the ipn post can take as long as a day.