The automotive environment is electrically very noisy, with potentially large spikes on the 12 V power bus (especially during engine start). This can be mitigated through the use of large filtering capacitors, maybe an inductor inline on the supply, and perhaps a transorb or other protection device. I don't know enough about power supply filtering to tell you exactly what to do, but you might be able to Google "automotive power supply filter" or similar. Note that the regulator may require input and output bypass capacitors, too.
Then there's the issue of iPad fast charging. I'm not sure how it decides it can draw more current for charging than what is normally allowed by the USB spec. I think there are resistors of a specific value between certain pins on the supply side. If you don't care about fast charging (which I've heard the iPhone 4 also uses), then you can ignore this.
You don't want to put an LED inline in order to see that power is being drawn. An LED has a maximum forward current above which its lifespan is dramatically shortened. This forward voltage is typically 5 - 25 mA, far less than the 1000 mA your regulator is capable of delivering (and far less than the 500 mA the iPod will likely draw). An alternative would be to set up a high-side current sense resistor (inline on the +5V side) and high-side current sense amplifier, use the output of that to drive a MOSFET or other transistor to turn on an LED. There are probably other ways to do that, but that's what comes to mind.
It really is easier to buy an off-the-shelf USB charger with a suitable input voltage, and cut off the supply connector to wire it in (with a fuse!) to your car supply. As another commenter mentions later, it may still lack appropriate filtering. You should be able to buy an automotive power filter to put inline with the USB charger. Then plug the Cables to Go panel mount into the charger.