If I can come up with a quick way to make my Palm 3 GPS "road-ready" I can test this. Is there a reverse-docking-connector I can buy somewhere to build a serial adapter from?

Oh, God, don't bother with that. Just open the thing and solder GND, RX, and TX straight to the PCB. It's dead-obvious which pins are which when you get in there. On the back side of the PCB (opposite side to the connector) you can see which pin is GND (it's one on the end and you can see it's GND pretty clearly from what it's soldered to) and the RX and TX are thoe only two other obvious traces on that side. Slight amount of trial-and-error for RX and TX ordering, and you're done.

Assuming your PCB is the same as mine was, of course.

Oh, and you need 12v to the power plug if you want to actually use it in the car. I just snipped off the connector end of the cigarette lighter cord at the point where it started to go from straight to coiled (this gave me about 6 inches of straight cable and the connector) and soldered the loose ends to the AmpRem and GND wires on my car's wiring harness adapter. And then I plugged that into the regular jack on the GPS unit. Or you could pull 12v and GND from the sled serial plug if your sled's serial plug is properly wired.

But if you're just doing it for testing purposes indoors, then just use the AC adapter for 12v, don't bother with power connections.