Kristin - Sure, happy to answer what I can. 

The term "Divine Service" is pretty unique to Lutheran circles and that is indeed the denomination I belong to. 

Wikipedia actually has a decent overview of the term. Much of it gets into specifics about the order of service but the "Definitions" section gives you the roots of the terms and how it's a continuation of the historic Mass that traditional Lutheran churches continue to uphold: http://en.wikipedia.org/wiki/Divine_Service

To get a flavor for how these elements of the worship service sound, the Lutheran Church-Missouri Synod website has audio files you can download and listen to: http://www.lcms.org/pages/internal.asp?NavID=15581

To your last question, that's very much the case. We receive God's gifts and are upheld in our faith through the right instruction in Law and Gospel as well as the gifts of the Sacrament. Then, as evidence of that faith, we serve others. Such service does not bring justification ("works righteousness" is a no-no since it's all Law with Christ's grace being diminished) but instead follows from a regeneration that is brought about through the Holy Spirit. 

Hope that helps. I serve on the Board of Elders at my church and we are deep into the study of the Lutheran Confessions and the historic liturgy, the former being where I'm drawing most of my answers from, if that helps explain where I'm coming from here.