I was working on this again the other night but I forgot to write down the chords. What I can tell you, for now is that I do it in Am and theres a G a D and an F in there somewhere.
For the first line use and A Minor shape with a Bass run down the 6th string start with Am then Am with a G bass, then with an F# bass and change to a D at the end of the line. If that's too complicated I think you can just play Am GMaj and D. If I get a chance I'll post a full set of chords some time.
The great arrangement on Niamh's album, including a lovely harmonica bit by Mick Kinsella, is credited to Graham Dunne. If you want to hear some fine traditional guitar playing listen to Graham and Denis Cahill playing together on two sets of tunes on Niamh Parson's "Heart's Desire" Album.