Not easy.

Here's what I've found:

Not in-game (yet) but you can do this easily by editing a config file.
Go to \Mind_Path_to_Thalamus\UDKGame\Config and open UDKInput.ini in any text editor you want.
Search for
Command="GBA_MoveForward"
and you should see the key bindings for movement. Replace the WASD keys with whatever you want you might. But you want to take care not to have multiple commands bound to one and the same key.

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Someone said that didn't work, so they edited all of these files:
Engine\Config\BaseInput.ini
UDKGame\Config\DefaultInput - Copy.ini
UDKGame\Config\DefaultInput.ini
UDKGame\Config\UDKGame.ini
UDKGame\Config\UDKInput.ini

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I just figured out how to invert look for the mouse and xbox 360 controller.

Mind_Path_to_Thalamus\Engine\Config

Open with notepad BaseInput.ini

then search this: ;ConsoleKey=Tilde

and delete the semicolon at the ';' (semicolon). That will enable the console.

Save the file.

Then ingame, open the console using the Tilde key and just type: InvertMouse 1

Then press enter ;)

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Alternate option.

Find in the same file:
Bindings=(Name="MouseY",Command="Count bYAxis | Axis aMouseY")

change to

Bindings=(Name="MouseY",Command="Count bYAxis | Axis aMouseY Speed=-1.0")

and that worked for me.
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Also, to invert the look on a 360 controller, find this line at the top of the file:
LookUpScale=-250
Change to
LookUpScale=250