At the risk of sounding like a Pharisee...

At the risk of sounding like a Pharisee I ask the following question about the Mass I was at this morning:

Would it be a liturgical abuse to substitute the words:

Hear our prayer, hear our prayer,
Through this bread and wine that we share
May we be your sign of peace ev'rywhere.

for

Lamb of God, You take away the sins of the world. Have mercy on us.
Lamb of God, You take away the sins of the world. Have mercy on us.
Lamb of God, You take away the sins of the world. Grant us peace.

The above 'replacement' for the Agnus Dei was then also sung as the Communion hymn. Now, I'm not an expert, but I don't think that should have been done. Any ideas?

I really would hate to have to criticize the Mass this was done in because Bishop Sheen was quoted and the Blessed Mother was mentioned in the homily.