push button start
if you use a switch along with a few relays, you dont need a key at all. use the switch and relays to power the accessory, ignition, and heater/ac wires.. and to start it, flip the awitch on, and push the button to start. to turn the car off, flip the switch off. I'd suggest using 3 switches for more control..
As for the first question, I would seriously not recommend using just a plain switch from radio shack, unless you want to have a fire hazard in your car. Theres a TXT file somewhere on this board that has the wire colors you need to splice into. If i remember correctly the Ignition wire is black with a blue stripe, and the A/C wire is blue (i might have those backwards). The color for the starter wire is in that TXT file, I'm at work now and I cant find it.