Repenting for you sins is a lesson learnt - you realise the error of your ways and will, hopefully, not repeat them, in this life or another. And while we don't rememeber our past lives (although some people claim they do), we do remember the lessons, which is why people have different character traits, etc - they have overcome issues that others have not and are now working on different issues.
I'm sure I've explained this terribly.... The ultimate aim is to be like OT Yoda, then when you die you can become one with the force. Yeah, Star Wars philosophy, you just can't beat it.
As for Christ, I 100% believe he came to Earth and said what he said. However, I believe he was misinterpreted. I believe when he spoke of his Father, he didn't literally mean his daddy the guy with the beard up in the clouds - he was talking metaphorically about the single universal mass that we are all born from, and all linked to (again, the force is a good simplification of the concept I'm trying to explain). And the whole dying for our sins bit, well I was talking to a bible thumper the other day and he told me that Jesus died for my sins. I asked him what that actually meant and he didn't have an answer (well, he did answer me, but his answer didn't answer my question at all - he was just quoting dogma). What does it actually mean? How did Jesus dying on the cross save my soul? I don't get it. There's no denying his self sacrifice was a fanatastic example of compassion and if we all tried to live our lives like Jesus did the world would be fabulous, but I don't understand what 'died for our sins' ACTUALLY means.