Lumen, I hope you continue this study. Even if there aren't a lot of responses, that doesn't mean no one's reading. I see it this way: because Catholics have Tradition and Magisterium, they tend to see things eye to eye with each other; and so, after the first few posts, everyone will agree or accept the minor differences and move on. This is opposed to a Protestant study, which can easily turn into a free-for-all brawl since everyone is his or her own pope.
I hope these continue, too - they're very interesting, and show very clearly how the two Testaments are connected, and how the Old prepares for the New.
Didn't the OT Jews already have the notion of a priesthood that had the power/authority to absolve sin? I'm referring to Leviticus 5:4-6 and 19:21-22 here.
The sacrifices for sin listed in Leviticus and the other books are for sins which are either due to the Law - such as touching a dead body, which is not evil in itself, and which most people would have to do at some point - or for sins of negligence. Leviticus 5:15 says "If any one shall sin through mistake...", and the rest of the sacrifices are similar. For intentional sin, the punishment was usually death by stoning, or exile from the community (which would most likely result in death), or, for some sins such as theft of animals, where restitution could be made, that was done (obviously, with sins such as murder, no restitution is possible, nor for something like sexual sins). In the New Covenant, even these sins can be forgiven through the Sacrament of Penance.