You can use the simple wordpress shopping cart with any type of PayPal account so this is not an issue really. As far as the integration goes… it’s really simple… all you have to do is enter your PayPal email address (you will get this after you setup the PayPal account) in the settings menu of the plugin.
I have posted a video tutorial on the following page that should give you a good idea of this (see the “Installation and Usage” section of that post)
http://www.tipsandtricks-hq.com/wordpress-simple-paypal-shopping-cart-plugin-768