to change the styles navigate to
menu > System > configuration > KDE > LookNFeel
you change the Style and Window Behaviour to your own and add choose from the packages you have installed.
That may help you a bit. however i kind of know what you meant by changing the theme, i think some where in themes.org they talk about something like a theme manager, but i havent seen it in mdk10.
However after you have installed the theme, some of the style components will be distribute to style so look there, thats the best i know.