I have a business and have written a book to provide some additional income.  I want to sell it as an ebook.  Buyers may be in NZ, but could also be in India, China or Europe, so I'm thinking that the currency would be NZD and USD as a minimum.  I want the buyer to be able to click on a link on my webpage, see a pic of the cover and a bit of a write up and then click to buy.  On receipt of payment the system would deliver the ebook to their mailbox.  I already use paypal as a credit card payment method for my business.  I've not done this before, so I would like some advice on the following:

1.  What format would be best, e.g. epub or pdf
2.  Any recommended payment gateways (the best I found for a reasonable price was Gumroad but they only offer USD)
3.  Recommendations for a publisher who can edit and proof read the document.
4.  Anything else I haven't thought of!!

Since this is a new venture, I'm keen to keep the price down.  If I can get some sales there is potential to grow it into a collection.

I would appreciate any advice you experts have.

Jo