In general here's one way to do it -
When your silverlight app loads check the URL for paramters - see the thread @ http://forums.arcgis.com/threads/10445-Is-it-possible-to-pass-arguments-in-the-URL for one way to get the parameters.
Take the value of the address parameter (e.g. '301 E CENTRAL ST') use it in a query task against the address layer in your map service. Take the geometry of the returned FeatureSet, add it as a graphic to your map & to zoom the map to that geometry.