1) go into the css file.  if you are going to use the default skin it will be in /portals/_default/default.css.

change this style in the CSS

body {background-color:Black}

This might cause things to look funny with the default skin because of the graphics they use for the inside panes.  You'll have to play with things.

2)  The "You are here" part is called a breadcrumb.  This is contained within your skin you are using.  The default skins should be located in /portals/_default/skins/MinimalExtropy.
You can always find out what skin you are using on your site by going into your Site Settings option on the site.  I think it is under appearance.

Anyways open the skin file you are using and take out the breadcrumb.  Should look like this:

<dnn:BREADCRUMB runat="server" id="dnnBREADCRUMB"  CssClass="Breadcrumb" RootLevel="0" Separator="&nbsp;>&nbsp;" />

The stuff below the bottom pane is another skin object.  This one is the link skin object:

<dnn:LINKS runat="server" id="dnnLINKS"  CssClass="links" Level="Root" Separator="&nbsp;&nbsp;&nbsp;|&nbsp;&nbsp;&nbsp;" />

Remove it if you want. 

Hope this gets you started.