I mounted the control unit under the forward floor console. Most of the wires you need to splice are right there under the dash. The unit I bought also had a remote starter, ign kill, and a few other things I didn't hook up. I only did the keyless remote, with the horn chirp and lights flash.
There are 2 relays located under the Pass side kick panel. These are the lock/unlock relays. A small harness comes from the old IR sensor in the headliner and connects to these 2 relays. Simply splice the lock/unlock wires from the new control unit into these. Then you only have several power cables to connect.
I found the Haynes manual wiring diragram to be usefull enough for this. You'll need a ohm/volt meter as well. The volt meter will verify the wires you use for power only have power when they are supposed to.
BTW: I spliced in my new unit while leaving the old circuits intact. The IR receiver is still in the headliner. This was just my personal choice.