Does anyone have experience in creating eBooks for the Kindle?

Im working from existing Word documents of text & diagrams (the diagrams may be removed).

Can anyone shed any light on the formatting though? Is it a straightforward file conversion from a finished Word document on an A4 page layout or should the text be pasted into something like WD on a specified page size so it is a .html file when complete?

The finished products will be for sale via a website. I don't own a Kindle either, so Im not entirely sure how eBooks appear on them.

Thanks