Hey ricker,
Good questions, and I'll try to answer them as best I can. I'll actually address your last question first.
Yes, the earthly sanctuary system were shadows. It is important to remember they were not shadows to become irrelevant after the cross; rather the earthly system was the shadow of the heavenly reality. Essentially, the earthly sanctuary system was God using props to show a fallen and degenerate human race exactly how he intended to save them. And of course Christ is the center of all of this.
What the cross actually was--the altar of sacrifice--is all a part of this sanctuary system. To imply that the cross and the sanctuary system are mutually exclusive is to not fully understand either one. Christ died once and for all on Calvary, forever meeting the blood requirement without which there would be no remission of sin. His sacrifice is complete, it is eternal, and nothing can be added to it. But as we know from the earthly sanctuary, after the blood of the sacrifice was spilt, it also was applied to the Holy Place, as well as the Most Holy Place once a year on the Day of Atonement. Trying to isolate either the high priestly ministry of Christ or his role on the cross at the expense of the other is to preach an incomplete gospel in my opinion.
My primary thrust in that paragraph is to emphasize that the cross is not adverse to the "sanctuary system" in the first place. It's the center of it!
As far as where from the Bible can this emphasis be found... I won't flood you with proof texts but the book of Hebrews is a solid starting point that lays a solid basis from the New Testament.
God bless,
Andrew