From what I can piece together, what is being said is:
Harley's Understanding of the Catholic's Immaculate Conception Doctrine
1) God wanted to come to man through the Incarnation.
2) He needed a vessel to do so.
3) God kept Mary from sinning so He could build a tabernacle in her.
4) God knew Eve wasn't up to the challenge so He didn't bother to keep Eve from sinning.
5) Our Lord needs 9 months R-n-R and wants everything just perfect in the human tabernacle; hence Mary needs to be perfect.
6) Mary's actions of saying, "...be it unto me according to thy word" is an error in the text and should read, "OK, fine with me.". Mary has free will and could have rejected the offer but God really knew (or at least hoped) that she wouldn't. Mary has to tell God that she is going to cooperate in His plan. After all, it is rather presumptuous for God to assume Mary will bow to His wishes even though He kept her from sinning all those years.
7) Nine months later the Lord Jesus magically *POPS* out (Ta-Da) upon a sinful world without destroying her virginity (which she keeps in tack for life). Mary and Joseph forgets the moment twelve years later when looking for our Lord Jesus and finding Him in the temple.
8) God kept Mary from sinning her whole life and Joseph has a hormonal imbalance that keeps him from wanting to consummate the marriage.
9) Mary simply saying "Yes" to God makes her the "Mother of God" (whatever that terms means) and thus she co-redeems the universe.
Did I miss anything? I wondered if simply saying "Yes" to God makes God really, really happy? Would that make Moses the co-redeemer of brush fires?
And you gave up being a Southern Baptist for this??? Oh, brother.