E-commerce: "selling" a form

I’m looking for a way to build a form in wordpress for e-commerce purposes. The plan is following.

1. customer clicks on the link, then new page with the form appears.
2. customer fills up this form, chooses some options (radio1 selected -> combobox 1 appers, radio 2 selected -> combobox 2 appears, etc..)
3. by the end of the proccess he submits the form and is prompted to pay using the PayPal.
4. Once the process is done – he waits for the response on the mail and site.

the “product” that he’s buying is the “link” to a file (which I will upload on FTP). as simple as that.

5. I, as the administrator, receive information that the customer has filled and send back the link when it’s ready.

I was thinking about using some e-commerce WP plugin, but products are usually “clothing”, “cars”, “mouses” i.e. “something that you can touch”. In my case, I’m looking for a way to sell a “form”.

Any suggestions about how to do it?