Welcome to the Wild World of X-Cart!
Now I'm sure someone will correct me if I'm wrong, but here goes!
In skin.css look for VertMenuTitle, VertMenuItems, etc.
Changing those should take care of you.
The PoweredBy X-Cart is found by going to....
"Edit Templates" (over in the right nav bar)
then look for "poweredby.tpl", edit away.
Hope that helps!
Rod