XCode4 Unit Testing and UIAutomation

I'm looking to set up testing at my company, but I'm a little fuzzy on the best way to start.

I know that I can use a framework for unit testing, such as OCUnit, GHUnit or SenTestingKit... so far so good. I can make a target which logic tests my project, using Mock objects etc.

I'm also aware of using UIAutomation and javascript to drive and test the GUI.

So, now if I implement a fairly complex GUI feature, I would like to logic test my code and also test the GUI using UIAutomation. How do I combine these two methodologies, or are they to be treated separately, in which case am I to assume that I need to write two sets of tests in two different languages to fully test one feature?

On a side-note, if anybody can provide good links for advice on beginning testing on an already mature and not-so-modular codebase, that would be much appreciated.

Thanks!