the firstway to play this song is to play these chords either open or with bar 
chords, chordssound better, in my opinion:

Intro: A(for two measures),D E

G (320003@1)CD
If I had a hammer
                  G (320003@1)CD
I'd hammer in the morning
                  G (320003@1) CI'd (x32010@1)hammer in the evening
              DAll (xx0232@1)over this land
              GI'd (320003@1)hammer out danger
                 CI'd (x32010@1)hammer out a warning
                C (x32010@1)   G (320003@1)      C (x32010@1)             GI'd (320003@1)hammer out love between my brothers and my sisters
C (x32010@1)          GC DAll (xx0232@1)over this land

G (320003@1)CD
If I had a bell
                   G (320003@1)CD
I'd ring it in the morning
                   G (320003@1) CI'd (x32010@1)ring it in the evening
              DAll (xx0232@1)over this land
             GI'd (320003@1)ring out danger
               CI'd (x32010@1)ring out a warning
              C (x32010@1)   G (320003@1)      C (x32010@1)             GI'd (320003@1)ring out love between my brothers and my sisters
C (x32010@1)          GC DAll (xx0232@1)over this land

G (320003@1)CD
If I had a song
                   G (320003@1)CD
I'd sing it in the morning
                   G (320003@1) CI'd (x32010@1)sing it in the evening
              DAll (xx0232@1)over this land
             GI'd (320003@1)sing out danger
               CI'd (x32010@1)sing out a warning
              C (x32010@1)   G (320003@1)      C (x32010@1)             G (320003@1)
I'd sing out love between my brothers and my sisters
C (x32010@1)          GC DAll (xx0232@1)over this land

G (320003@1)CD
Well I've got a hammer
               G (320003@1)CD
And I've got a bell
                     G (320003@1)CAnd (x32010@1)I've got a song to sing
              DAll (xx0232@1)over this land
                   GIt's (320003@1)the hammer of justice
                 CIt's (x32010@1)the bell of freedom
                     C (x32010@1)   G (320003@1)      C (x32010@1)             GIt's (320003@1)the song about love between my brothers and my sisters
C (x32010@1)          GC DAll (xx0232@1)over this land

Good luck with the song
if you still have to ask you please report gmx.net under my e-mail address a.staerker@gmx.net

Regards alex