If you can manage web design with Dreamweaver I think you will find Sigil and epub creation easy.
That is the voice of a non expert on the matter as I just use Sigil for tidying existing books up. However, the following was my experience and may give some credibility to that claim
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I have a little, but long ago, simple programming experience (just a little Fortran at university and then a little simple playing around with Basic ) and had never bothered getting much familiarity with HTML at all. A few years back I had a short try with Dreamweaver to try designing a web site but decided the learning curve for that was far more than it was worth to me.
Later, for ebooks, I was introduced to Sigil; straight in, no problems to get to grips with it and found it quick and easy to edit existing books to make them more presentable to read almost straight off. I haven't done much creation of books (have done a few very simple ones from plain text, including with images, end notes, etc) but I can see the learning curve for that is short and easy for non complex layouts. Cruising this site was also a big help, as was looking at some of the better presented books in the mobileread.com ebook uploads.