yes i think it probably would juice dande greens. although i must say this, growing wheatgrass outside is the easiest damn thing you will ever grow. i mean you just have to literally thro some seeds out the window and come back in a week!! look at molly bloom's recent post in the wheatgrass forum to see how easy it is to grow lots of wheatgrass outdoors.
the design of that metal hand crank juicer you linked is very similar to the design of the omega juicer you already have. however, the metal is better at squeezing out more juice than the plastic omega is, although exactly how much more juice you would get out wit the metal one versus the omega i couldn't really say.