Assuming that the adapter that allows you to simply plug RCA plugs into the CD-Changer port works (ISTR that Kenwood changed their protocol at some point and the adapters they sell now don't work with older units), then, yes, that would work. As far as power goes, you'd just splice the two units wires together, so that both of them draw power from the same wire provided by the car and both of them use the same signal to switch on. One possible problem is if your car's wiring can't handle the power requirements for both units, but I don't remember hearing any real-world reports of that actually occurring.

Oh, and usually, the most difficult part of installing a new stereo, IMO, is getting it to fit in the dash properly. The wiring should be fairly easy.