Yes. Apostle John's answer is clear that those things recorded on the Holy Bible is enough for us to believe that Jesus is the Christ, the Son of God, and that by believing we will receive the promised salvation.

That's why, Apostle Paul taught the members of the true Church of Christ not to go beyond what is written.

6Now, brothers, I have applied these things to myself and Apollos for your benefit, so that you may learn from us the meaning of the saying, "Do not go beyond what is written." Then you will not take pride in one man over against another. (I Corinthians 4:6, ibid)

And they are reminded not to add anything nor take away words from what have been written and those who add or take words away from what are recorded will receive punishment from God.

18I warn everyone who hears the words of the prophecy of this book: If anyone adds anything to them, God will add to him the plagues described in this book. 19And if anyone takes words away from this book of prophecy, God will take away from him his share in the tree of life and in the holy city, which are described in this book. (Revelation 22:18-19, ibid)

Therefore, it is not true that the Bible cannot be the sole guide to salvation, because the Bible can make us wise for salvation. It is not also true that the Bible does not contain the complete truth about Christ, because what are written on the Bible is enough for us to believe Christ and be saved through our faith in Him.

So, if you want to be saved on the day of judgment, believe in the truth recorded on the Bible, just like what the members of the true Church of Christ did.