I think you could set up a sandbox account and test with that without having to upgrade and pay any fees. Yes, you would change the TestMode variable that controls weather our script submits to the regular or sandbox API.
As long as you have a "Pay with Paypal" option, which uses express checkout, then those people wouldn't have to share their billing information with you. The people that pay with credit card on your site would of course have to give you their correct billing address.
Did this help? Tips are appreciated...
