Hi Bob,
I try to think of where the Apostles were coming from to better understand their teachings. What I mean is a lot of the NT Scripture is directed towards the Jews, because that was who they 'first' went to and that is why you here so much about the law.
Also at that time they were teaching something 'new,' that indeed the Messiah had come and was crucified and raised from the dead. This was a profound new truth that they were trying to get out to the world at that time. Now the gospel of Christ has been spread and heard by most in the world (I say most only because of the possibility of some few may have not heard). But the Apostles were at that time just trying to get people to understand and believe that indeed Christ had come and had raised up from the dead, as proof of who He was.
Rom 10:9 that if you confess with your mouth the Lord Jesus and believe in your heart that God has raised Him from the dead, you will be saved.
At that time believing was the first step necessary, but this was just the beginning for any of the true elect. Now sure there could be those who said they believe that were not an elect at all, it is also necessary "to believe in your heart," I think that only comes with the Holy Spirit indwelling... think about the parable of the sower and the seed.
Now do not think that anybody can just die before God has a chance to finish fully preparing that one for the first resurrection. Understand that God is not in some kind of race to prepare a person before they die... He is in control of these things to start with and calls a person exactly when He has made them ready to accept the truth and then really has no time limit to finish what He has started in them.
Php 1:6 being confident of this very thing, that He who has begun a good work in you will complete it until the day of Jesus Christ;
Basically God does use a teacher, as in that Scripture about the Eunuch you mentioned, to bring somebody to these teaching, as we all had Ray for that. But not only does the Holy Spirit open your eyes to understand the truth, but I do not believe that a teacher is absolutely required for the rest of that believer's life. Indeed it is the Spirit in us that can and does show us the truth by any means that God desires.
John 14:26 But the Helper, the Holy Spirit, whom the Father will send in My name, He will teach you all things, and bring to your remembrance all things that I said to you.
But I certainly believe there is the necessity for all believers to go through a process of living and preparation and to not only believe that Christ is the Savior, but also come to 'know' Christ.
John 10:27 My sheep hear My voice, and I know them, and they follow Me.
That following Christ is the process needed in every believer to produce fruit, through learning and living by righteousness.
Mat 7:20 Therefore by their fruits you will know them.
v. 21 "Not everyone who says to Me, 'Lord, Lord,' shall enter the kingdom of heaven, but he who does the will of My Father in heaven.
1John 5:18 We know that whoever is born (begotten) of God does not sin; but he who has been born of God keeps himself, and the wicked one does not touch him.
v. 19 We know that we are of God, and the whole world lies under the sway of the wicked one.
v. 20 And we know that the Son of God has come and has given us an understanding, that we may know Him who is true; and we are in Him who is true, in His Son Jesus Christ. This is the true God and eternal life.
mercy, peace and love
Kat