PsychoticEpisode
Christianity doesn't have a very strong philosophical framework - like for instance you encounter many problems when you attempt to determine what is our relationship with god, what is our relationship with the material world, what is our relationship with other living entities, what is our relationship with this body, what is our relationship with hell and of course as you indicate what is our relationship with heaven (by heaven I assume you mean the eternal abode of god, as opposed to an elevated sphere of material enjoyment)
(that said it tells you how to approach god, but perhaps is a bit sketchy on a few details of why)
You die, while awaiting judgement you swear to God that you accept JC as your personal savior, the gates swing open and in you go. Pretty simple, right? Its the place to be. No revolving door, just one way.
Probably not quite so easy as that, but ok, for arguments sake we will accept that we have arrived in heaven
Is it just me or is there a common conception that heaven and all its occupants live(?) a sinless existence?
true - sinful life is characteristic of th e material world and conditioned souls
Except for Lucifer getting the boot, and whether he sinned or not is still debatable, heaven doesn't seem like a place where a lot of sinning goes on.
The root cause of sin is to be socialized around ignorance, and ignorance is the bodily concept of life, and th ebodily concept of life is meeting the demands of one's material body (or things related to the body, like my family, my country, my race etc) - in heaven living entities are socialized around the spontaneous loving service of god
What happens if your soul or whatever sins in heaven?
Sin doesn't happen in heaven - the moment one develops envy of god is the moment one appears in the material world - in other words one falls down from heaven the moment one conceives that there is no pleasure in heaven. This has implications for persons striving to achieve heaven - if you are not socialized around the spontaneous loving service of god in this life it seem s dubious that you will arrive there in the next, since even if you did you wouldn't like it.
Is a heavensent soul even capable of sin?
generally the living entity is described as marginal, which means there is the tendency to fall into illusion as well as the tendency to become liberated
Once in heaven can you be sent to Hell?
Generally your first destination is an elevated material post, after which anything can happen
Or is eternal happiness guaranteed once you pass thru the gates?
generally it is understood that we only require the experience of falling from heaven once, just as a child can learn that an iron is too hot to touch by one experience
Is there anything that guarantees you stay in heaven for an eternity?
A good attitude towards the other person (god) characterized by service - the same thing required for maintaining a relationship between any two people
Does one leave the sin part of an existence outside the gates? Is sin something you can't take with you once you enter heaven?
There are no notions of enjoying seperately and independent from god - the number one enjoyments of the material world are sex, possession of opulence and false prestige (Imelda Marcos, the wife of a dictator famous for having an extensive 1000+ collection of designer shoes, said something interesting once - words to the effect that the standard enjoyments of this world are sex but the only reason people are satisfied with such paltry engagements is because they have not tasted power) - these things are absent in heaven - of course it is inconceivable to the conditioned soul how something could be more enjoyable than these things, but there are scriptural statements of liberated personalities from heaven expressing their surprise that people can find pleasure in these things
Are all traces of humanity left behind?
No - humanity is refined - animalistic propensities are left behind
Personally, if there is such a place as heaven then I see no reason why the human souls that get there can't resume their sinning ways.
they can - no problem - the living entity is created with free will - the living entity is not free from the results of their activities however - generally though we are intelligent enough to only require one sojourn to the material world to be convinced where the real benefits lie.
It seems as if our souls, even though they are with us from day one, are suddenly sinfree or incapable of sin once in heaven? Why the sudden change? What hocus pocus takes place to unburden the souls going to heaven?
You are right - being qualified to enter heaven is not so cheap - as far as the most common method to arrive in heaven is concerned, it requires not to be socialized around sinful activity (either pious or impious karma) - since this is a difficult ask for the conditioned soul, it is a process that could theoretically happen in a moment, but practically happens over a period of many lifetimes -how many depends on us
BG 7.19: After many births and deaths, he who is actually in knowledge surrenders unto Me, knowing Me to be the cause of all causes and all that is. Such a great soul is very rare.