Can the gloria and sanctus be replaced at the Mass with some other hymn or song? Can the gloria and sanctus be replaced at Mass with some other liturgical hymn or song?
Or can they be partially modified?
General Instruction of the Roman Missal (2003):

53. The Gloria is a very ancient and venerable hymn in which the Church, gathered together in the Holy Spirit, glorifies and entreats God the Father and the Lamb. The text of this hymn may not be replaced by any other text.