We use the COM object solution that uses Server.CreateObject()
You can find the lines of code where we create and use the pfpro com object.... there are probably only 4 or 5 lines of code and they are in the include file named after the pfpro service.
Then find a code example for how to do pfpro in ASP using the new system. You should be able to find the corresponding 4 or 5 lines and update them. I believe it involves using MMHTTP instead of the COM object but I haven't actually seen any code examples of how to integrate the new paypal system with ASP, but I'm sure paypal will provide you with that information.