I am not sure I can offer much help about the actual publishing process through Amazon. I just use it as a marketplace. I published the book myself. I had it printed with a local printer who were extremely helpful, showing me different styles and weights of paper and covers, and advising me about page margins. (my book was of craft projects, not fiction, so I wanted it bound in a certain way).
I laid it out with Microsoft Publisher because I needed to draw diagrams, then just saved it as a PDF to send to the printers.
I needed photographs and am not a good enough photographer myself so I paid a friend who is semi professional.
Because I had photographs I could use one for the cover but for yourself if you have an idea of what you would like a couple of ideas might be to:
Ask local camera clubs if anyone would either sell you one of their existing photos or take one for you.
Have a look at local makers markets for photographers and artists who might like the commission.
If you need illustrations how about contacting your nearest art college?
You don't need an ISBN number but if you want one it might be easier for you to go to Amazons recommended seller and save yourself the hassle that I had.
Marketing:
You really need to blow your own trumpet even though this may go against the grain.
Have you had any short stories published in magazines ? If so, they will probably do a book review for you.
When things are back to normal, groups like the W.I. are often looking for speakers, you could offer to talk about your experience of self publishing. Take copies of your book with you to sell.
Your local library might do meet the author sessions you could ask to be included, same if you have a local independent bookshop.
I really enjoyed putting together my book and the whole self publishing process, but be under no illusion that I made a profit! I don't think I even covered the costs, even taking into account fees for giving talks. But it was really good fun so all the best to you and good luck.