So what pointers has John given us? Lots, but here's a few to be going on with:
We've already seen that John refers to the miracles as signs: signs pointing to who Jesus is. The Eerdmans Bible Dictionary says that "Biblical miracles are never just conjuring tricks, but are bound up with the work of God in history for his people's salvation and with the understanding and acceptance of his message." They don't stand alone - they have purpose beyond the immediate. Signs.
Tom Wright reckons there are six signs in John's gospel (water into wine, the nobleman's son, the paralysed man at the pool, the loaves and fishes, the man born blind, Lazarus) but that the sequence shouldn't stop there: John harks back to Genesis 1 as the gospel commences, where on the seventh day all was complete. The seventh sign is thus the completion of the work: the crucifixion of Jesus, from where Jesus calls "it is finished!". The word that is translated "it is finished" (teleo) is the word people would write on a bill when it had been paid. It is done, it is complete, it is paid. It is finished.
No.
The death of Jesus is our route to Salvation. Nothing more is needed. As we'd say in mathematics: it is necessary and sufficient, i.e. it is what you need and it is all you need. His death opens up the way to God. He died and the gap between heaven and earth was closed. To put it simply (because I said it was simple): Disobedience to God is sin. Our sin stands between us and God. Jesus died in order to remove our sin. Nothing need stand between us and God anymore.
The trouble with simplicity is that it's the implications of that simplicity that are far-reaching. It's a simple truth that God exists: but look at all that follows on from that!
But what if this simple truth - Jesus dying for our sins - isn't true? You may recall Paul's statement in 1 Cor 15:19 that, if Christ were not raised from the dead then we are to be pitied more than anyone else. So how much more are we to be pitied if Jesus' death isn't true? How much more if what Jesus accomplished on the cross isn't true. In short, if Jesus did not die for our sins, then we are wasting our time, completely utterly, thoroughly and we may as well give up and go home now. (Nobody moved - good).
So, if it's true - who is the message for? Jesus said that you don't send a doctor to the healthy, but to the sick (Matt 9:18, Mk 2:17, Lk 5:31) and so this message is for those still unforgiven - us, in a small part, but more those "out there" who haven't yet responded to this good news. I used to do Good Friday walks of witness and we always put the question: "what's 'good' about Good Friday?" To which we gave the answer: Jesus died for our sins. It's good news and we therefore shouldn't keep it to ourselves. The church is not a secret society - it's an open society. Any barriers are of our own making, for Jesus blew the real ones away on the cross. He said in 6:37 "all who come to me I will not turn away", so the barriers are in our choosing, not in His receiving.
John takes great trouble to make us aware that Jesus' death took place at Passover, so we ought to start there. Passover is recorded in Ex 12 and Num 9. The first interesting thing I found was that the Passover lamb could be a sheep or a goat (technically a lamb or a kid). This will be important in a moment. The Passover lamb (or kid) was slaughtered and the blood daubed on the doorframes of the houses that the Israelites lived in, so that the angel of death would pass over these houses and not strike down the first-born. And thus did Israel escape slavery in Egypt. In commemorating the Passover, everyone joined in - even those ceremonially unclean (who normally couldn't celebrate feasts), albeit a month later. Aliens living amongst the Israelites could celebrate it, but to not do so meant that you had to bear the consequence of your sin. John equates Jesus clearly with the Passover lamb, even down to no bones being broken (as for the lamb, so for Jesus), quoting Exodus 12 and Numbers 9 in doing so. John also, as we've seen, has a different timeline to Matthew, Mark and Luke so that at the point at which the Passover lambs were being killed in the Temple, Jesus dies, thereby enforcing this symbolism. Jesus - the Passover lamb. To not partake is to bear your own sin.
The other scripture John quotes at Jesus' death is from Zechariah 12:10. It's a passage that goes on to say that "on that day a fountain will be opened to the house of David and the inhabitants of Jerusalem, to cleanse them from sin and impurity". Death that leads to cleansing.
The third Old Testament concept I'd like to look at is the scapegoat: it's a word that's entered our language (as is true of many Biblical things) to mean "one that bears the blame for others" (Merriam-Webster online dictionary) but comes from Lev 16:7-22, where the high priest (Aaron) laid both hands on it, confessed all the sins of Israel over it (he may have been there for some time) and laid them on the goat's head. The goat then carried the sins away as it was released into the desert.
Now you may well say, as I first did "but Jesus is the 'lamb of God', not the 'goat of God'", but as the Passover lamb could equally be a goat, I think this idea holds up OK.
Moving into the New Testament, we see two things: repentance and declaration. Repentance is a turning around, a commitment to change. It is a response to the offer that Jesus places before us. It's not necessarily easy - see the discourses between Jesus and Nicodemus and between Jesus and the rich young ruler for evidence of that - but it is, I believe, a requirement.
Finally, the declaration: Paul, writing in 1 Cor 15:3 quotes a very early formula "Jesus died for our sins", which was traditional within only a few years of the crucifixion. It wasn't an idea that grew up over time, appeared long after any original witnesses to the crucifixion had died or was determined by a council once the church was established. It was so close to the crucifixion itself as to be reliable.
So, I believe that Jesus died in our place, taking our sin upon himself. His death both removed our sin and protected us from the wrath of God. But this is an offer - which we can choose to accept, or reject. As Paul put it in Romans 6: "the wages of sin is death, but the gift of God is eternal life in Christ Jesus our Lord". As with all gifts, you can chose not to accept them.