I did some with Createspace a few years ago - they only go through Amazon though.
Draft2Digital really does seem to have it made - though they don't have a connection to paper publishing at the moment, which is the only downside I've found so far.

i suggest checking out their website and reading everything they have to say about publishing through them and give it a shot!

If you want to start off doing a chapter-by-chapter approach and do the whole thing after you get "there" - then Dbooks.org is a great place to do it - though they do still have some difficulties/conflicts with non-Word office programs. I use LibreOffice myself and have to use my HTML coding skills to make their editor work correctly - but it does sync well with Steemit.

just a couple of thoughts. I think the best bet is to dive in and give it a shot.