macOS selling an application help

I have a problem here. So far my applications have been freeware, but now I've just finished one I think I can sell... I want to at least give it a try. The problem is, I have no clue how to sell it. I am a registered developer for macupdate and can put apps up on softpedia as well. But neither website handles selling your application like I am used to on the palm. I have a paypal account, and iweb. How can I set up a system to automatically email people who purchase my product, sending them the full version? (I'm doing file fulfillment since it's the easiest)
Any help would be greatly appreciated.
Thanks in advance, Nate

@ ironduke - Thanks, but that leads to another question. What's the easiest way to set up a button that will allow them to donate? Sorry for these probably stupid questions but all I know is my paypal name.

@ darkroom - Thanks I will check those out