When making the book available as an ebook does this affect the availabilty of the paperback version? Also does it detract from publishers credits?
Finally, can it keep the same ISBN?
When you make your book available as an ebook, you are basically creating a new edition of your book. This doesn´t in any way affect the availability of your paperback, it simply means that customers have another option when it comes to buying the book.
You publish and revise an ebook edition exactly the same way as with a paperback edition, which means you have to use a publishing credit each time you want to replace the file being released to customers.
It can´t keep the same ISBN as it is a different type of book and therefore a key field in the book details will be different. However, it doesn´t necessarily need an ISBN at all. If you have already made it available on Kindle then Amazon have it. We don´t need you to have an ISBN to sell it on CompletelyNovel.