How do I replace the default messaging icon in the dock with handcent?

I've a Samsung Galaxy S with 2.2 firmware. I'm using handcent instead of the default messaging application. In the default messaging app settings I have disabled notifications and disabled auto-retrieve. But when I get an SMS now, even after I had read it in handcent, I still get the new message notification overlay on the messaging icon on the homescreen until I click into it. Can i disable this, or better yet replace that icon with handcent?