Three-column design: one static header, one side-bar with v-scroll, one center-box with v/h-scroll

Answer 1

A Grid with two rows and two columns. One control in cell 0,0 with a RowSpan of 2. Each of the other controls in cells 1,0 and 1,1 respectively. Row 1 is sized absolute and Row 2 is percentage sized. How you govern the display of scrollbars is up to your design and what controls you host in the grid.

Update

I believe you just need to host your StackPanel instances inside ScrollViewer instances. This should give you the scrollbars that you need.

Answer 2

I haven't tested this so there might be a typo or two but it should point you in the right direction. The ScrollViewers will place the scroll bars and will figure out whether to display vertical and horizontal scroll bars based on the size of their content. There are also properties that allow you to specify whether you want are scroll bar in each direction but I've found that the automatic detection usually works best.

<DockPanel LastChildFill="True">
    <ScrollViewer DockPanel.Dock="Left">
        Left Pane Content
    </ScrollViewer>

    <TopPaneContent DockPanel.Dock="Top" />

    <ScrollViewer>
        Main Body Content
    </ScrollViewer>
</DockPanel>

I just noticed the Silverlight tag. To use a DockPanel in Silverlight you'll need to use the Silverlight Toolkit. Instructions on how to add it are here and you can find it here.