If you set up the DNN Nav Menu using the RenderMode attribute, you can get the menu to render as an unordered list of links, which you can then style. Something like:
< dnn:nav id="dnnNAV" csscontrol="mainMenu" providername="DNNMenuNavigationProvider" runat="server" >
< customattributes>
< dnn:customattribute value="UnorderedList" name="RenderMode" / >
< /customattributes >
< /dnn:nav >
You will need to use CSS to get the menu to appear the way that you want it to appear.
If you want to do this, but also save yourself some time, install Mark Allan's DDR Menu (dnngarden.com). It is a replacement for DNN Nav, renders an unordered list, but also provides several different (and very customizable) menu styles for you.