Formatting for Kindle is doable; to format for Nook, you need to understand some computer gobbledygook, or so it appears to me. The Nook formatting guidelines are indecipherable. So I see the value of Smashwords more and will let them do it all, save for Kindle.
Why the world doesn't work on one single operating system -- call it SOS! -- is beyond me.
Doing the cover yourself is sort of fun, but in my case, there are limitations. I downloaded a free PhotoShop-like application, but not the instructions (too long, don't care to read) so can't do that much with it. Still, I used it for a swell lighting effect. Here's what the cover looks like (title/name obscured for now; you'll just have to wait):