Mary, Martha, and the Good Samaritan?

Yesterday I heard a short talk on the story of Mary and Martha in Luke 10.38–42. I've spoken briefly about this passage myself, so this isn't an unfamiliar story for me. I have to admit, however, that I had never read this story in its textual context. In fact, I find it a little discomfiting that the immediately preceding story, the Parable of the Good Samaritan, is actually one of my favorite stories to speak on, and yet I had never considered its effect on its literary neighbor! And this despite my criticism of those who read Luke's account of this parable apart from the discussion in 10.25–28, of which the Good Samaritan is the answer.

So the question I have, and which I would love to get some response on, is this: How do the stories of (a) the Good Samaritan and (b) Mary and Martha inform and balance each other? How can Jesus, according to Luke, go immediately from telling a story in which the failure of those serving God in the Temple serves as the foil for the Samaritan's service to a stranger to a story in which Mary's failure to serve Jesus and her other guests is praised, even above the service of her sister, Martha?

As a potential spoiler, the speaker yesterday morning likened both stories to the two commandments of Luke 10.27: Love the Lord, and, Love your neighbor. The Parable of the Good Samaritan is, in this light, commentary on the second commandment, while the story of Martha and Mary is commentary on the first. I like this reading, except that at least as it was presented yesterday it depended on the parallel text in Matthew's gospel, especially the reference to "the first and greatest" and "the second" commandments. I don't think Luke had Matthew 22 in mind. So how, within the dynamics simply of Luke's gospel, do these two traditions inform one another?