[Cvengr]

If the Jews don’t need Christ, then who is preparing the annual sacrifice for the atonement of their sin by the most strict sacrificial system?

[Mr. M.J.B.]

“If the Jews don’t need Christ,...”

Short answer:

Judaism is a complete religion on its own - long, long before others came along; it is still complete. It has no need for another religion’s gods.

Judaism doesn’t claim another religion’s texts either, which precludes insurmountable and irreconcilable differences.

Hopefully this more fully answers your questions about korban.
http://www.jewfaq.org/qorbanot.htm