How do members of the Church of Jesus Christ of Latter-Day Saints reconcile an unchangeable God with the concept of eternal progression?

Book of Mormon 9:9-10 states, > 9 For do we not read that God is the same yesterday, today, and forever, and in him there is no variableness neither shadow of changing? > 10 And now, if ye have imagined up unto yourselves a god who doth vary, and in whom there is shadow of changing, then have ye imagined up unto yourselves a god who is not a God of miracles. This seemed to me, on recent pondering, to be in some conflict with the idea of eternal progression taught by the Church--the idea that, rather than eventually just sitting on our laurels and singing in a celestial choir for the rest of eternity, we must always continue to learn, grow, and improve ourselves. Implicit in this is the idea that God Himself is also on this path of eternal progression, though I welcome correction if I am reaching beyond where there is sure doctrine. Is there any statement or argument to reconcile these concepts of unchangeability and progression? ***I would prefer a response that is absolutely, unequivocally doctrine accepted and taught*** by all the First Presidency and Quorum of the Twelve, but since that is frequently unavailable for questions as esoteric as this, I'm also interested in other quotes, theories and musings from earlier Apostles, logical arguments--whatever I can get.