The Greek word translated here ‘guide’ – and it is a perfectly proper translation – is actually a little more literal than that: He will lead you into all truth. If you are guided, it can suggest you just need some help, some direction.
But did apostles write all the New Testament books? Were there not others besides apostles who wrote? Yes, there were New Testament prophets. We read about them in the letter to the Ephesians, chapter 2 and 3. There were prophets inspired also, but the apostles must authenticate what is in Scripture. Oh, you ask, was that not left to a church council, or three church councils actually, in the fourth century to decide and to affirm which books were in the canon of Scripture? And the answer is, no. The apostles decided which books were inspired. They knew; they were inspired to know. We do not know exactly how or where these things were determined, but when the era of inspiration ends, the books of the Old Testament and the New Testament were firmly sealed under apostolic authority. And what church councils did later on with a measure of human wisdom was merely to confirm that, and it was all decided within the inspiration of Scripture and it was decided by the apostles.