How do I use the functions.php to change the widgets in my sidebar?

I have just upgraded my wordpress from version 2.5.1 to 2.7 and everything looks great so far.
Now I need some help, in my earlier version I used the plugin TTFtitles and it seems to work just fine now. But this plugin just gives you nice titles of yor posts and pages, I want nice titles in my sidebar so in version 2.5.1 I changed the wp-includes/widget.php file. All the functions called wp-widget-XX($args) has been altered and it’s the same code that has been changed in all of them:

<?php echo $before_widget; ?>
<?php echo $before_title . the_ttftext($title) . $after_title; ?>

I also changed the default array in the register_sidebar($args = array())

Now I want to put this in my functions.php file instead, but how do I do that?
I tried to put the functions just as they were in my functions.php file but that didn’t work naturally…
I tried to send an array with the register_sidebar() by writing

if ( function_exists('register_sidebar') )
	register_sidebar(array(
		'name' => sprintf(__('Sidebar %d'), $i ),
		'id' => "sidebar-$i",
etc...

But I couldn’t make it work.

So I do I do this? How do I make it work? Is there anyone who can help me? Tell me how I must write this code? I know that I can do this in the functions.php file instead but I don’t know how!
I can add that I use two sidebars.
Thank you for your help.