You can do it with standard payments....you basically construct a paypal form, include a pass-through variable like the username and you include a return page, its is all sent to paypal where they make their payment, then they are returned to your landing page. Paypal will also dump to a .php file of your choice all the variables, so that you can put them into your database.
I did this exact thing last month...just sat down with their materials and figured it out. The Paypal sandbox is great for testing.