About the "spirit of" Vatican II

From the Catholic Encyclopedia, we have this definition:

Ecumenical Councils are those to which the bishops, and others entitled to vote, are convoked from the whole world (oikoumene) under the presidency of the pope or his legates, and the decrees of which, having received papal confirmation, bind all Christians. A council, Ecumenical in its convocation, may fail to secure the approbation of the whole Church or of the pope, and thus not rank in authority with Ecumenical councils. Such was the case with the Robber Synod of 449 (Latrocinium Ephesinum), the Synod of Pisa in 1409, and in part with the Councils of Constance and Basle.

To emphasize: "...the decrees of which, having received papal confirmation, bind all Christians."
We are taught that the councils are guided by the Holy Spirit, and are, therefore, protected from error. Again from the Catholic Encyclopedia:

All the arguments which go to prove the infallibility of the Church apply with their fullest force to the infallible authority of general councils in union with the pope. For conciliary decisions are the ripe fruit of the total life-energy of the teaching Church actuated and directed by the Holy Ghost.

So how, exactly, are we to understand the "spirit of Vatican II"? 
First, unless we reject the infallible authority of the council acting in union with the pope, we must accept that the documents published by the council, particularly the constitutions, are the full expression of the council's intention on their respective subjects.
Second, to properly appreciate what was intended, we must commit the time and energy to read and study the documents, and to seek out scholarly commentary on them.
Now on having followed those steps, which must, I think, be viewed as acts of conscience, we may then consider the representations of those who propound various actions in the name of the "spirit of Vatican II". We can then evaluate them, as follows:

1. Do the proposed actions agree with declarations made by the council?
2. Do the proposed actions appear to be contrary to the declarations of the council?
3. Is there commentary from the Vatican already on the sort of changes proposed?

Few of the champions of the "spirit of Vatican II" I have met have been aware of the fact that the council's constitution on the liturgy (Sacrosanctum Concilium) affirmed the use of Latin, and further, strongly affirmed preference for Gregorian chant in liturgical music. There have been subsequent documents on the liturgy (see Liturgiam Authenticam) and on sacred music, which provide cautions and guidance. There are more than those to which I have linked, but they are a good beginning.
Liturgiam Authenticam addresses the issues surrounding translations of liturgy to the vernacular languages. Although Sacrosanctum Concilium, in my reading, seems to allow for the vernacular in the context of mission lands, not the entire Church, this has been softened in recognition of the fact that the vernacular, however badly implemented, is now pervasive.
The best commentary on the liturgy, and on its abuses, is in The Spirit of the Liturgy, by then Joseph Cardinal Ratzinger. I have read a review of Vatican II: Renewal within Tradition, edited by Matthew L. Lamb and Matthew Levering, and will soon read that volume, as it appears to be a very clear discussion of what we should properly understand from the documents of Vatican II.