Download-able sale, help please


It has been really long time since Ive been here. Always good people who are willing to help. I have a question. My shop is closed but fully functional and ready to go online at any time. I was thinking to sale along with domain. However, I realized I can use it to sale photos for download. I have already shop so it makes things easier at least it seems easier but is not. Could someone who use CS cart give me some idea. I mean, I really dont know where to start to make this work. I know change goods for pictures is easy, but this is not enough. My shop lucks PayPal as well. No idea why.

My questions are:

  1. how easy is to re-brand shop?
  2. where should I start?
  3. how to control download link to make available only for certain time
  4. let`s say someone purchase 4 photos with different size (3MB, 10MB, 30MB) where do I put them on server and how Paypal redirect buyer to download link (links?)

    If anyone have more idea I would very appreciate it

    Thank You