<<<and at what price are holders of NRGP shares converted to NRGY shares? >>
They are converted at a ratio not a price. You get .77 shares of new NRGY for each share you won of NRGP. The new price will be whatever Mr. Market says they are as of that day.
"Under the terms of the merger agreement, NRGP unitholders will receive 0.77 NRGY common units in exchange for each NRGP common unit they own at closing, representing a premium to NRGP unitholders of approximately 10% based upon the 20-trading day average closing prices of both securities ending August 3, 2010. "