I did a DD rail conversion on my G&P and had to get a different barrel nut for it.
Here it is...
http://shop.ehobbyasia.com/madbull-d...l#.U1SWUn-taRM
As for the wrench, it is not included. You can either get the Madbull one, or the SPEED one (fully adjustable for any sized barrel nut or buffer tube nut)
http://shop.ehobbyasia.com/madbull-a...l#.U1SXLn-taRM
http://shop.ehobbyasia.com/speed-cnc...l#.U1SXRn-taRM