Atheism is the disbelief in God, which really means the lack of 'faith' in God, which really means not trusting God...
Of course modern atheists actually deny any kind of deity whatsoever. But that is really just a symptom of a very temporo-spatially-restricted metaphysical incapacity - the inability or unwillingness to think-about first things.
From the Fourth Gospel (written by the Beloved Disciple often called John) it is clear that if we have Jesus, we have everything - and Jesus is with us each directly in the person of the Holy Ghost.
Jesus is what brings eternal life - Heavenly life as children of God destined to a similar quality of divinity as Jesus himself (if we want it); and it is Jesus in whom we must have the same trust as a loving child of loving parents. A trust based-upon direct personal knowledge, personal contact of a spiritual kind.
It's really very simple, and is there for the asking. But we must ask. This gift is not forced-upon us. Heaven is only for those who want to be there, who love to be there.
(Historical evidence suggests that such persons may be a minority, and perhaps a small minority. This self-exclusion is very sad indeed for those who love the self-excluders. They will be missed greatly, and the gap they leave cannot be filled. All we can do - but this would should do - is try to ensure that they make their decision based on truth about the nature of the gift.)
It is really very simple - terrifyingly so, in a sense... And of course it changes everything - just as being the loving child of loving parents changes everything by contrast with being a feral child, or the resentful child of coldly-exploitative parents.
It changes everything - forever.