A lot has happened since I last checked this thread, but regarding Jamie's last statement ("it's painfully unclear") it's important to remember what FlemGem said above: the Bible is a story. I take issue with Christians who talk about how the Bible makes life really easy, or it's an instruction book with all life's answers in there; it is about a relationship. Those are complicated enough with two human beings over a short term, much less a tale of an omnipotent creator and the entire human race over all history.
But in another sense, as I hope I explain below, it's both simpler and much harder.
Also Jamie in reference to this statement you make, referring to my discussion: "the New Testament "replaces" the Old Testament" I suppose I should be clearer, differentiating the collection of texts which comprise the new and old testaments with the larger conception of a testament or covenant with God. Christ fulfills the old law, overcomes death and sin, and gives us a new way to live and love God.
Here are a few examples of how this is discussed in the New Testament. At the Council of Jerusalem, described in Acts 15, the council described how Christians did not have to become Jews first (specifically the question involved circumcision) and gave a set of rules that people still disagree about (my own inclination is that they prohibit only partaking in the most improper, degrading, and cruel aspects of idolatrous pagan behavior at the time) but which are certainly separate from Jewish law.
Part of this decision is based on the vision God gave to Simon Peter, which is earlier in Acts: God commands him to eat unclean foods, but Peter protests that he has been kosher all his life; Peter understands that this means that what God has cleansed no one should call unclear. So while the old Laws may have been necessary to maintain ritual or moral purity, we no longer need those things. Christ has made clean all things.
To continue a tour of my favorite passages of the New Testament, Paul takes this concept to its highest point in I Corinthians: he tells us that there's all sorts of awesome stuff God gives us, the "more excellent way" is love, superior to all things as the truest expression of God. 1 Corinthians 13 tends to be the one people know as "the wedding Bible verses" (it was said at my wedding so I am not casting stones) but it's much larger than that. Prophecy, tongues, wisdom, all fail, but love is forever. Paul compares this to a maturing human being: the toys of a child are useless to the full grown adult. Elsewhere Paul compares the Law to a tutor, but now that we heirs of God have grown up we have no more need of it.
So just as you would still use some of the things you learned while young, so too would you use some of the Law. But it's all judged in the context of love. This is actually way harder than even the most complicated and byzantine legal rules, because ultimately any of us truly loving one another is beyond human ability; fortunately, we are not alone in this. God loves us and he teaches us to love.