There were more webpages on the internet than people on the earth almost 10 years ago now. So don't be so worried about there being to much of anything on the internet, there is. Really this can be turned into a positive if you think of it like this: all the similar sites to yours are just potential link partners!
Health and Wellness will through eternity be one of the biggest marketing areas, so don't discount the validity of your idea, it is a good one.
If you are looking for way to get a site started p.m. me and I can show you some places to start getting web content out there for free or cheap, right away.
As far as your ebook, I would just
sign up with
google accounts and start writing a word doc with all the articles you put on your website. When you have enough you can simply save your document from google as a pdf file and viola!