Your requirements are rather demanding. If i can summarise:
- silverlight will be the front end (or container)
- you don't know what it will be showing
- the content may be dynamically generated
- everything, including the visual content, will be retrieved from the server
If i have misunderstood then by all means correct me or adjust your question.
Those requirements are not trivial, especially when you have no prior experience in Silverlight. Fetching data from the server is a normal behaviour in Silverlight, but fetching any generated UI content will be a slow and inefficient use of the technology platform. Silverlight is delivered via the browser, and runs on the client. If you are going to have generated UI, then you may want to consider using straight HTML instead (you can generate the contents using ASP.Net or a scripting language such as PHP). Alternatively, you can generate your required UI views from within the Silverlight app itself by either swapping in and out the appropriate pre-built piece of UI (or controls), programmatically adding new controls into the visual tree, or by loading XAML using the XamlReader class.
This answer may or may not help you much, but like i said before - put some more specific details into your question and you will get more specific answers (either add comments under your question, or post a new more specific question if you cannot edit your current one).
Edit: i have just come across this blog article from Jeff Prosise explaining the use of the INavigationContentLoader interface in Silverlight 4 to dynamically load pages from either remotely or locally. It is a detailed write-up, with a lot of code samples, it may be of use to you.