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It doesn't require you to have a canon law/theology/history degree, but the essentials are not that difficult to grasp. You need valid Mass and sacraments. You need the truth, the truths of the Faith, unadulterated. You need a real priest.

But how do you know what Masses and sacraments are valid? how do you know what is the true, what unadulterated the truths of faith are, and if a priest is or is not a real priest? How do you know what is required for a priest to be validly ordained?  

But how do you know what Masses and sacraments are valid? how do you know what is the true, what unadulterated the truths of faith are, and if a priest is or is not a real priest? How do you know what is required for a priest to be validly ordained? 

If you can't reason through it own, and you're not necessarily required to if you don't have the ability to do so, then you just pray and ask God to lead you to valid priests and valid Sacraments.  He will not refuse such prayers offered in sincerity, since Our Lord taught that even we who are evil will not give our children a stone if they ask for bread.  As for "unadulterated truths" of the faith, I think some groups have to get off their high horses in pretending that their conclusions are "of faith".  Theological bickering can occur all within the confines of what Holy Mother Church has defined and taught.  For the average person, if you are not inspired to think past it, simply knowing the Catechism suffices, along with the formal intention to believe everything that the Church (actually) teaches [not something that one or another Trad group "hallucinates" (an AI term that's rather aprorpos here).

In the entire world of Trad controversy, there are really only two issues that touch upon the faith, and where some Trads are slouching toward Old Catholicism, where you attribute the evils of the Conciliar Church to the Catholic Church.  You're better off in a "sede-doubtist" stance, saying, "I don't know.  It's above me to figure it out."  There are alternatives to dogmatic R&Rism (which +Lefebvre did not ahere to despite how hard some modern dogmatic try to pretend he did), but where he actually agreed that the Pope is guided and protected by the Holy Ghost and cannot do these things.  +Lefebvre unequivocally affirmed that proposition, and if you doubt this, that's where you're going off the rails into heresy.  Now, the reason he did not publicly (at least) come out as a sedevacantist was because he realized that the SV syllogims had some minors that dogmatic SVs ignore, such as ... could one or another of these putative popes be under duress (control, blackmail, etc.) where their acts wouldn't be free acts and therefore null and void.  Father Chazal has an impoundist position that's perfectly Catholic.  Key is that we cannot attribute these grave evils to the Magisterium and the papally-approved Universal Discipline (Mass, Canon Law, etc.) of the Church, since that would be tantamount to asserting that the Church had in fact defected.

Now, the other key dogma is EENS, "Extra Ecclesiam Nulla Salus", "no salvation outside the Church".  While the Church has long tolerated the opinion that there can be a Baptism of Desire, and within strict limits, BoD doesn't have to be fatal to Catholic ecclesiology, but if you extend BoD outside of catechumens and the like, i.e. to Prots, Orthodox (an absurdity of course since they are validly baptized), and even infidels like Jews, Muslims, and "Hindus in Tibet" (+Fellay-ite nonsense, since there aren't any Hindus in Tibet, or at most one or two lone wolves) ... once you say that those can be saved, you have a monumental problem for Catholic ecclesiology.  Once those are to be considered able to be saved (obviously without converting, since anyone can be converted), then since there's absolutely no salvation outside the Church, you must say they were somehow in the Church, anonymously, without knowing it ... and most Trad clergy adhere to "Anonymous Catholic" soteriology.  If you do that, then Vatican II's ecclesiology, that most Trads denounce as heretical, ceases to be problematic, and the Trads who believe that non-Catholics can be saved have no business rejecting V2 ecclesiology.

But those are the two pivotal issues that are in fact of faith ...

1) the degree to which the Cathoilc Church can officially promulgate evil (teaching, universal discipline)
2) EENS and ecclesiology

dogmatic R&R run afoul of #1 and have become thinly-veiled Old Catholics

99% of Trad clergy believe that non-Catholics can be saved, and most believe that even infidels can be saved ... and thus have no business rejecting V2 ecclesiology

But those are the two pivotal issues that are in fact of faith ...

1) the degree to which the Cathoilc Church can officially promulgate evil (teaching, universal discipline)
2) EENS and ecclesiology

dogmatic R&R run afoul of #1 and have become thinly-veiled Old Catholics

99% of Trad clergy believe that non-Catholics can be saved, and most believe that even infidels can be saved ... and thus have no business rejecting V2 ecclesiology

The real problem is nobody in the Trad movement understands infallibility. It is a mystery how not a single person in the entire Traditional movment can grasp this basic doctrine, including you.   The second problem is that apparently, nobody in the Trad movment understands the traditional Catholic teaching on the ways in which a person can be united to the Church.  Because of this ignorance, people in the Trad movment think that, what is now called "partial communion," is a novelty of Vatican II.  

Question for you: Do you accept the Traditional teaching, according to which a Protestant (i.e., someone baptized and raised in a Protestants Church and never received into the Catholic Church) can be saved if they are in good faith?