The gospel which we preach nowadays, which I refer to as “the gospel of salvation,” is largely about leading people to a salvation experience, typically in the form of “the sinner’s prayer.”
But such an experience is entirely lacking from the ministry of Jesus. Certainly, there’s nothing even remotely like a “repeat after me” prayer in scripture, but more, Jesus never called on people to perform any sort of act of conversion: no sinner’s prayer, no pledge card, no “with every eye closed, raise your hand.” Nothing. Nada.
So apparently, instead of a sinner’s prayer, the transition from sinner to saint was changing how you thought about God’s kingship, re-working your worldview and your view of Heaven. And that was between you & God; no public declaration, embarrassing or otherwise.
And since He demonstrated it, regardless of what we think of His teachings, we have to admit that “the Kingdom” the way Jesus sees it includes healing the sick and raising the dead. We watch Him in the Gospels, and it *looks* like it involves hanging out with tax collectors and “sinners” more intentionally than going to “church” (in his case, Temple).
And apparently, judging from the way he announced it, it involves thinking differently. And since he was talking to arguably the most religious people in history, apparently it meant “think differently than your religion has taught you.”
Adding His teachings into the description, the “good news” [“gospel”] of the Kingdom appears to also include loving people outside our comfort zone, and replicating ourselves (“bearing fruit”), and being treasured by God (as in the Pearl of Great Price).
It may be of some benefit to just look at every place that the Kingdom is mentioned in the gospels (start here: http://bit.ly/KingdomGospels), and see what the Holy Spirit shows you. But take your time; there are 119 verses in that link, each with some revelation on the Kingdom.
I very much encourage you to discuss what you learn with Holy Spirit, and let Him separate the meat from the bones!
Does that offer any help understanding the difference between Jesus’ term “the gospel of the Kingdom” (Matthew 4:23) and our unscriptural term “the gospel of salvation”?