Of course you should! The different voltages come on different LPC pins. See this diagram:

As you can see, the VCC 3.3V and VCC 5V are on different pins (Note, this diagram is of a 1.0 xbox from the top, but you egt the idea)
As for the 3.3V point, show your installer these:

vs.

Tell him it should look like the first one and not the second (For 3.3V anyways).
Thanks appleguru, of course how silly of me, the voltages are on different pins that makes perfect sense. I guess my head was swimming with all this to take in at once. As for the 3.3v, the top most photo is the one I took to the installer, so that's how things should be done. Anyways this weekend I'll crack my box and take a peek to see that's how it was done. Thanks again.