it jsut plugs into the back using the OTHER cable supplied... GM11 I think it is.
It has a pigtail that lets you plug it in and also has the female side of the socket like the oem head so you can reconnect your OEM accessories.
You flash the firmware using a USB cable and your home computer. Software is supplied on the website.
You install the chip by completely disassembling the unit, draining the capacitor by shorting it with a srewdriver, and carefully removing an existing circuit board and replacing it with a newer one you purchase separately from PAC.
My suggestion? wait until they start including the update in the retail version... they will probably have one soon that says "iOS4 compatible" or "iPhone 4 compatible" on the packaging just like they did when the new 5v only charging scheme for the iphone 3g, nano 4, and Itouch 2g came out.