The place to start is the General Instruction of the Roman Missal (GRIM). The fourth edition marked March 27, 1975 is the current document. The GRIM like the Roman Missal is written in Latin. The English translation is prepared by the International Commission on English in the Liturgy. Like most Vatican documents it is available on line here.
In the last decade or so the Roman Catholic Church has begun to enforce compliance to the GRIM by Ordinaries, that is bishops, and their priest, especially in the United States, where certain illicit practices had crept into the Mass. Some of the practices were carried out in ignorance, with the best of intentions. Others were not originally illicit, as they were carried out under indults from Rome, which have expired.
Most of these deviations were small in nature, but collectively impact the reverence of the Mass. Most have to do with individuals exceeding the boundaries of their prescribed roles. The GRIM says:
All in the assembly gathered for Mass have an individual right and duty to contribute their participation in ways differing according to the diversity of their order and liturgical function. Thus in carrying out this function, all, whether ministers or laypersons, should do all and only those parts thatThat means there are parts of the Mass only a priest can perform. Other parts normally the province of a deacon, if one is present. And other parts relegated to lay ministers.
belong to them...
belong to them...
For example if there is a deacon present it is his role to proclaim the gospel. The priest will not read the gospel if there is a deacon present, that role only relegates to him if there is no deacon.
Likewise the reader(lector) will do the first and second reading and also lead the Psalm, if there is no cantor. The GRIM specifically opens this role to women.
No one questions that only the priest can perform the Consecration. In the same way only an acolyte, deacon or priest can perform certain task in the preparation before and the purification of vessels after Communion.
Since the revision of the Mass there has been more than one translation of the Missale Romanum into English. This has resulted in what to some seems a never ending tinkering with the Mass. Be advise that the original Latin has not changed. The changes to the English are a result of an effort originally to use a more colloquial translation, which was unsatisfying in its adherence to the specific meaning of the Latin.
One of the results of this was a controversy over the pro multis translation. It is part of the Rite of Consecration of the wine. In Latin the phrase means for many. In the original Latin the priest says: “Qui pro vobis et pro multis effundetur.” In the current English translation, the priest says: “It will be shed for you and for all.” "For all" in Latin is pro omnibus.
This is a translation with theological impact because while Jesus died to bring salvation to all mankind, salvation is only granted to those who follow Him. A person can refuse salvation. That is the prerogative of free will. So in truth his blood "will be shed for you and for many," but not "for all."These changes are not going to happen overnight. The appropriate authorities are determined (finally) to get a proper stable translation that Rome won't second guess them on (again.) So don't expect to see these changes for a few years.