Salvation is by faith, faith in Christ. That "decision" in and of itself will bring change in a person's life. The resulting change is what people refer to as repentance.
What happened to Zaccheus? He believed on Christ. And then??
Here is the fruit of repentance:
Luk 19:8 And Zacchaeus stood, and said unto the Lord; Behold, Lord, the half of my goods I give to the poor; and if I have taken any thing from any man by false accusation, I restore him fourfold.
Faith came first. It wrought a great change in his life. What kind of publican would do what he just did?
DHK,
I view Zacchaeus as being engaged by God's purpose to become first curious, then take to climbing a tree for a better look, and ready to respond favorably to the Lord "gladly" (Luke 19:6). It was a work of God's instigation and not human engineering.
Now most certainly, Salvation is by "grace through faith." Not doubt. Who has the grace and faith? Humankind? nope. It is the "gift of God."
The "decision" is not of human effort, for the Scriptures (as you know) are clear that there is no effort of humankind that can attain such authority (John 1).
Rather, such decision is oratory coming from an already changed heart. One does not confess and then get saved, one is saved and then confesses. This is the sequence of Romans 10: "for with the heart a person
believes, resulting in righteousness, and with the mouth he confesses, resulting in salvation.
DHK, we could both show many verses to support our view, but ultimately, what does John 3 say:
“For God so loved the world, that He gave His only begotten Son, that whoever believes in Him shall not perish, but have eternal life. “For God did not send the Son into the world to judge the world, but that the world might be saved through Him. “He who believes in Him is not judged; he who does not believe has been judged already, because he has not believed in the name of the only begotten Son of God."
So John 1 shows that not all have the ability given, only those who do not turn from the light are given the power. That such power is not innately within the capacity of humankind, but is given directly and specifically by God. That such a gift by God results in belief. (John 1:12 & 13)
The ultimate question then comes to resolve on whether human effort is what saves or is it authored and finished by God?
There are those who would use popular phrases such as "put your faith in Christ," and even quote the Scriptures, "Trust in the Lord with all your heart." And, I suppose that some may be convinced in their mind that such is a plan to follow and a way to think. But, such ultimately fails the test of the heart.
For as you have pointed out, the truly saved will pour out true repentance from a changed heart and mind. And DHK, as you know, such a change cannot take place outside of and without the "power of God (John 1)."