How do I modify the layout for the stock Dialer in Android Froyo?

So after making a few test apps that don't do really much of anything I think I am ready to try something more useful. What I would like to do is make a small layout change to the stock dialer on my Samsung Fascinate.

I don't want to change the core functionality, just make a small change to how the contact info is presented when selecting a number to dial.

I think I开发者_开发百科 need to update /system/app/dialeractivitytab.apk

I'm not really sure where to start though. Is this going to be more difficult than I think it is?

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You can't make changes to an existing app unless you have the full source code. If this is a samsung specific app, that source is probably not available. So yes, this is going to be difficult.