In my opinion no one source can give you everything you'll need to make this business plan.
Plus E-Commerce is quite a general topic. Let us know what your business sells specifically if you'd like some really great detailed reports about your market over the past 5 years, and insights for the near future.
That being said, a good business plan should cover all of the concerns of your current business model, as well as a lot of considerations for the future that you'll need to research in different locations around the web.
