migrating to ArcGIS Viewer for Flex 3.6, layerDefinitions and url parameters

Hi all, finally I have time to migrate my old viewer (1.3 :rolleyes:) to the last viewer 3.6.
I'm studying how to implement old capabilities and I find it difficult to figure out how to make the core functionality of my old viewer ... that launch a URL with a parameter that the viewer interprets, performs data filtering layer by setting the layerDefinitions and Search querying the SearchWidget...
Anyone already implemented this function or can drive me to the right way?
Thanks,

Naty