Uncle John's Band is really neat as a duet. Mando plays lead lines at the openning and the break, guitar plays chords throughout doubled by the mando. You can play it with 2 finger open chords so its pretty easy. I simplify it a bit, particularly the guitar chords at the break. Don't know if you know the tune, but Buffett's Distantly in Love is another great mandolin guitar duet, I think its off of One Particular Harbour and its pretty much DGA progression. Final recommendation, Copperhead Road by steve Earl.
If everyone demanded world peace instead of a new television, there would be peace. #John Lennon