Wow, you actually ask very informed questions! But... to be honest im too lazy to type out all of this...it would take me pages and pages to do thoroughly.... I do believe i have a good informed answer for you though. Im gonna do my best, but if I leave something out email me alright? I wouldnt mind at all :P Actually, not to sound like a creeper, but this is something i feel you actually need dialogue to talk about; i'd like to actually talk.... but like i said, i'll do my best.
I'll start with what it means to be "born again". The problem is, most christians dont know how to answer you so they revert to their "christianese" and parrot back what they hear in church. So.. Born Again...
Scripture says that we are spiritually dead in sin (for the sake of time, I'm not going to include references, but i encourage you to look it up, or email me in you cant find it). Birth marks the start of a life so thats a metaphor for saying that person is finally freed from the bondage of sin (because scripture tells us we were slaves to our sin—dead to anything spiritual) and can start their life in Christ. Born again... get it?
Now... how do you know if you're going to heaven?... Don't you think you'd know if something like that happened to you? The rebirth is when you surrender your old life. You are dead to that life—no longer the person you were. Everyone's done wrong. Everyone has sinned. Everyone's done something their ashamed of... God cannot tolerate sin because that would violate his perfect, sinless nature so sinners cannot be with him. So basically we're all screwed because we have to die to pay for our sins (the wages of sin is death—thats in romans 7 i think, without looking). However, God sent his son, the perfect, blameless sacrifice to carry the sin of the world. We were given jesus's good credit, his righteous life, while he was marked by the sin of the world. And he died for it and satisfied the law. (think of aslan on the stone table :P) However... Death has no power over the might of christ and he conquered the grave.
If you have ever done anything wrong ever—just one thing—you're a sinner. In fact, thanks to Adam, you were born with a sinful nature. Its part of who you are to sin.
"We aren't sinners because we sin, we sin because we're sinners." --(my bible teacher)
Just like fish will swim, man will sin.
So, now you realize that you need atonement and you surrender your life to serving the perfect will of Christ. I don't know about you, but when I think about the love God's showed us, dedicating my life to him is the least I can do... besides that, he can probably run it better than me. So now, after the rebirth, a christian spends the rest of their life going through sanctification.
Rebirth: the absolute rule/ power of sin is broken, but NOT totally removed, by the atonement of God.
Sanctification: The life long process a christian goes through in which they try and live their life more like christ's example. They cling to every word that comes from the mouth of God and walk with him daily and the power of sin is lessened with time (this is usually what it means to "grow as a christian") , but still not totally gone.
The Death Of Sin: Comes with our death when we rejoin the father in heaven. It's the final transformation. Our wills are perfect, our hearts and minds are perfect, we are completely rid of sin.
Now... What will we do in heaven? Well, Earth is God's creation and he said "it was good"..... GOOD. Imagine what perfect is like! Our spiritual bodies will be just as real and vibrant as our earthly bodies. More so even. We are "vapors in the wind" on earth; we are fleeting. We are called to glorify God by all we do and we will be forever worshiping God. But does that mean praying 24/7? Singing all day and night? No! God gave us talents! God gave us personalities! Is it glorifying God any less if a soccer player is using the body God made him to worship him? of course not! I'm not sure what God will be like, no one is, but it talks about a city.... Would there be a city if all heaven was was an eternal choir practice?
The difference is that, in heaven, there is no sin. Sin hurts people. The wages of sin is death.
Oh yeah! And im not sure where it says in in the Bible... but somewhere along the way, I heard that there would be feasts even though we wouldnt NEED to eat. We will cuz we want to :P Who says our bodies wont be physical? maybe they wont, but they'll be more real than our bodies now.
Oh thats right... you asked something like... 'How do i feel knowing christians are going to heaven and everyone else is going to hell?" Right?