Did He or did He not complete His Word so that we may know all things related to spiritual living, and so that we might use it as a guide to discern what is of God and what is not?
No, He did not. And where did I learn this? The Bible. Paul says that the SPIRIT was given to us for that very reason.
For to us God revealed them through the Spirit; for the Spirit searches all things, even the depths of God. For who among men knows the thoughts of a man except the spirit of the man, which is in him? Even so the thoughts of God no one knows except the Spirit of God. Now we HAVE received, not the spirit of the world, but THE SPIRIT WHO IS FROM GOD, THAT WE MIGHT KNOW THE THINGS FREELY GIVEN TO US BY GOD. 1 Corinthians 2:10-12
Peter says that GOD'S POWER has given us EVERYTHING pertaining to life and godliness.
seeing that His divine power has granted to us everything pertaining to life and godliness, through the true knowledge of Him who called us by His own glory and excellence. For by these He has granted to us His precious and magnificent promises, in order that by them you might become PARTAKERS OF THE DIVINE NATURE, having escaped the corruption that is in the world by lust. 2 Peter 1:3-4
John says that the anointing of the Spirit is what teaches us all things and is the reason that we KNOW God. This anointing is not some come and go sort of thing (as is often taught), but John says that it "abides" - lives, dwells or remains - in us.
But you HAVE an anointing from the Holy One, and YOU ALL KNOW ... And as for you, the anointing which you received from Him abides IN you, and you have no need for anyone to teach you; but as His ANOINTING teaches you about ALL THINGS, and is true and is not a lie, and just as it HAS taught you, you abide in him. 1 John 2:20,27
John also wrote:
By THIS you know the Spirit of God: every spirit that CONFESSES ("to say the same" - a true agreement) that Jesus Christ has come in the flesh is from God; and every spirit that does not confess Jesus is not from God. 1 John 4:2-3
This doesn't tell us to check people's DOCTRINE out so that we can compare it with scripture, nor is it suggesting that we listen for a specific phrase, such as, "Jesus is Lord" or "Jesus Christ has come in the flesh" since such a thing can be memorized and used as the "accepted answer". What it does suggest is that since those who are of God have had this anointing of the Spirit they cannot HELP but to have it's reality come out in their words, and that we are to listen for this agreement that Jesus Christ is the union of God and man, that this MAN, who was born of the Spirit, is the one who has brought us into fellowship with God through his blood.
I know how to twist these passages so that it seems to indicate that Paul, Peter and John were saying that the BIBLE was given so that we might know the things of God because it is exactly what I used to believe and teach. I also used to think that anyone who did not hold to this teaching just did not believe the Bible. The irony in this is that the more I was teaching that everything we needed was in the BIBLE the less I was seeing that everything is found in CHRIST ... and my words reflected that lack. The more I respect what the Bible says the more I see that it tells me that it is NOT my life, but it testifies very clearly that CHRIST is my life.