i would imagine that the switch for the heat control would be on the dash some place but seeing that i don't own a limited i can not tell you for sure where it would be located. but for the rest of your problem ....i would look at the leather seats and the cloth ones and see what wire are the same ( color code wise) ,i'm betting that the 2 wires you would normally hook up are there in the wire harness on the new seats .just match up the colors and splice in some new wires ....like if you had 6 wires all together and you only need 2 of them , then cut those two and take the old harness off of your old seats and wire it in like that .
now you would be able to disconnect them with the harness that came from your old seats instead of cutting ALL of the harness's from all the seats ( new and old) and also the one on the floorboard .
edit : ok looking at mine and the diagram below fixxer gave ... dg ( dark green is 12+) and black is ground . ............. any dark green and black on the harness ?