Adding Customizable / Flexible Header & Menu in Europe Free theme

Hi, I am figuring out like days on how to add customizable header in my this theme (currently using it). I have tried this one from WPLift’s blog . but failed. It warned me w something called ‘header is sent by….bla bla..error in wp-includes/pluggable.php at line (dont remember: maybe 128, 3700)’.

I uninstalled europe theme, n upload a new one. My blog alive.

Help me! I just wanna have header in my blog! A big one.