/What does sin mean to you?/
To me, sin is a kind of imperfection or ignorance. It is not necessarily something very bad, ugly or untouchable. In the process of evolution we are aiming at perfection, but right now most people are still wallowing in the pleasures of ignorance and self-indulgence. As long as you remain in ignorance, you will do things wrong, you will commit sins. But you must not feel that you are completely lost or covered in darkness. You are just, progressing from less Light to more Light, and ultimately to liberation from ignorance-imperfection-sin.
/How does one get liberated from sin? Does liberation happen suddenly?/
One can liberate oneself from sin only by invoking God's constant grace. God's grace always descends abundantly and powerfully, but most human beings do not try to receive it. If the individual wants to free himself or herself from ignorance, and cries to receive God's compassion-rain, then definitely he will be liberated from the snares of imperfection-sin. But this liberation comes gradually as the seeker becomes more illumined. You must not expect sudden and miraculous overnight transformations, although these do occasionally occur.