IMHO: don't !

now, it all depends on a lot of factors I don't know anything about : your age, your physical shape, and so on ..
You say you have never hiked before .... 15 miles a day on a non flat terrain is quite a lot for a non sportive type...
But OTOH if you are a marathon runner ..... <img src="/images/graemlins/grin.gif" alt="" /> ... it's a piece of cake !

Anyway, even if you're in a great physical shape, I second Goatrider warnings : your brand new equippment (especially, but not only, shoes...) do need some "training" before such a hike !