I've seen rice syrup solids at the LHBS. That would be the easiest way to get rice in there. Do a search of the forums for using uncle ben's instant rice in the mash.
Great Divide is pretty secretive about their recipes. I've asked for a couple recipes from a few different employees and have gotten stonewalled. With an adjunct like rice, I would use 5-20%. If using rice syrup, add to the boil. If using instant rice I'd add 1/2-1lbs of rice hulls for the sparge.
If I had to guess, I'd say probably 85% base grain, 10-5% rice, 0-5% specialty grain. Maybe Carapils. Or do a higher mash temp, maybe 154? Their beers seem to me to have a lot of body. I would hop with a similar BU:GU ratio as a wheat, so .33-ish. 15-20 IBUs