Turbolapp: modifying that stuff is usually just an issue of either replacing the graphic with your own and/or finding the element in your CSS file and trying different things to make it look good.
Of course, it helps if you know CSS... how to use padding, bold, margin, borders, floats, etc...
If you give me something specific to look at I'll try and help out. One easy trick people don't use enough is to look at your page in the browser and VIEW SOURCE to see what the browser is actually spitting out. A lot of times it will give you the info needed to know what to change/tweak/modify in your CSS based on the div/class/tables, etc...