Dear Omar:

If your friends are generally accepting the other paragraphs but are hedging on paragraph 841, then I think that paragraph 841 is getting misinterpreted.

Paragraph 841 does not say that Muslims are saved. It is talking about the fact that Muslims "can" be saved in the same way that any non-Christian can be saved, when through no fault of their own they do not know to join the Catholic Church. Muslims, like Jews and Protestants, have a special closeness to the Catholic Church because we all worship the God of Abraham. But this common denominator does not remove the need for Christ and His Church (the Catholic Church) to be saved.

Muslims are not saved by Islam; Jews are not saved by Judaism; Hindus not not saved by Hinduism, Buddhists are not saved by Buddhism. These people will not and cannot find salvation in those religious systems. Salvation can only be found in Christ and His Church.

The normal method of salvation is by being a card-carrying member of the Catholic Church. Non-Catholic Christians and non-Christians come under the "no fault of their own" clause.

But the dogma of the Church is that Salvation is through the Catholic Church alone. God, of course, can save those whom He pleases through extra-sacramental ways. That is the gist of Church teaching.

Paragraph 841 is based upon Lumen Gentium, 16 which reads (I have included scriptural and other footnotes):

16. Finally, those who have not yet received the Gospel are related to the People of God in various ways.(Thomas Aquinas, Summa, III. q8, a.3, ad1) There is, first, that people to which the covenants and promises were made, and from which Christ was born according to the flesh (cf. Romans 9:4-5) : in view of the divine choice, they are a people most dear for the sake of the fathers, for the gifts of God are without repentance (Romans 11:28-29). But the plan of salvation also includes those who acknowledge the Creator, in the first place amongst them are the Moslems: these profess to hold the faith of Abraham, and together with us they adore the one, merciful God, mankind's judge on the last day. Nor is God remote from those who in shadows and images seek the unknown God, since He gives to all men life and breath and all things (Acts 17:25-28), and since the Saviour wills all men to be saved (1 Timothy 2:4). Those who, through no fault of their own, do not know the Gospel of Christ or His Church, but who nevertheless seek God with a sincere heart, and moved by grace, try in their actions to do His will as they know it through the dictates of their conscience -- those too may achieve eternal salvation (Letter of the Sacred Congregation of the Holy Office to the Archbishop of Boston). Nor shall Divine Providence deny the assistance necessary for salvation to those who, without any fault of theirs, have not yet arrived at an explicit knowledge of God,  and who, not without grace, strive to lead a good life. Whatever good or truth is found amongst is considered by the Church to be a preparation for the Gospel and given by him who enlightens all men that they may at length have life.  But very often, deceived by the Evil One, men have become vain in their reasonings, have exchanged the truth of God for a lie and served rather than the Creator (cf. Romans 1:21, 25). Or else, living and dying in this world without God, they are exposed to ultimate despair. Hence to procure the glory of God and the salvation of all of these, the Church, mindful of the Lord's command, "Preach the Gospel to every creature" (Mark 16:16) take zealous care to foster the missions.

To simplify this document what the Magisterium is saying is that

But the plan of salvation also includes ... Those who, through no fault of their own, do not know the Gospel of Christ or His Church, but who nevertheless seek God with a sincere heart, and moved by grace, try in their actions to do His will as they know it through the dictates of their conscience -- those too may achieve eternal salvation

I should mention something here. Do not be caught in the trap of "where is that in the Bible." Not everything is in the Bible, nor does everything have to be in the Bible. To assert that notion of sola scriptura is, oddly enough, unBiblical since the Bible itself says that not everything is in the Bible (John 21:25, also Paul quotes a saying of Jesus that is not in the Gospels at Acts 20:35) and that Tradition (with a capital "T") is also authoritative (1 Cor 11:2; 2 Thess 2:15) and that we are to shun people not acting according to Tradition (2 Thess 3:6).

God's Revelation of Himself is found first in Sacred Oral Tradition and secondarily in Sacred Scriptures. Sacred Oral Tradition came first before there was a New Testament, before any apostle wrote any letters or Gospels. In fact, the determination of which manuscripts circulating at the time were actual Scripture and which were not were largely based on whether the manuscript was consistent with Oral Tradition of the Church.

See the Catholic Answers articles Scripture and Tradition and Where's Your Authority.

I hope this helps.

God Bless,
Bro. Ignatius Mary