Hi
To change the header font, open style.css and look for line 70, that begins:
h1.blog-title, h2.blog-title
just after the first { , enter something like font-family:arial; (or whatever you want the font to be. But remember people will only see the font if they have it on their PC, so stick with something generic.
To change the header colour, again look in style.css for line 80 that begins:
div#header
Where is says background:#000000 url(headers/defaultheader.gif) no-repeat scroll right top; , the 000000 represents the colour black in hex. If you change that to another hex code, the header colour will change (see http://www.crispgraphicdesign.com/hexcolorchart.gif for examples).
Hope this helps!