JOHN 3:16 says it all.
We can thank God that He gave the Catholic Church the authroity to declare, definitivley, that John 3:16 is the word of God - otherwise we would not know it to be so!
While it is an important verse, it is clearly and undoubtedly lacking in details (as God Himself realized when He willed that the Catholic Church also declare definitively that there were 4 entire Gospel books (and many other NT books) that man should become familiar with in order to know, love and serve Him (in addition to this one short sentence known as John 3:16).
So, I would strongly disagree that John 3:16 says it all.