I am planning on doing a Valentine One install soon and doing the same sort of thing. If I were you I'd goto radioshack and get yourself a multimeter. You will want a switched power source, of course unless you want your detector on all the time. Using the multimeter you'll fine the wire you want.
I ended up wrapping the hot lead around the right side 'prong' on a fuse that protects one of the electric windows from the passenger side fusebox. The detector is now activated via the ingnition. All systems go!
Here in Virginia, radar detectors are illegal. They aren't necessary in Northern Virginia, either. There's an "impeding the flow of traffic" law here. I'm certain that if you aren't exceeding the speed limit by at least 10 mph, you'll be ticketed for impeding the flow.