You can actually use your existing factory wire if you want to make your life a little easier. Other than that, it is no more difficult than power, ground, remote, RCAs, etc. for your subwoofer amp.
I actually know someone who put a 150 x2 RMS amp on his factory speakers in a Chevy Silverado Pickup Truck. He has the gain turned all the way down and surprisingly, the factory speakers actually sound OK with clean power. I won't say they sound great, but I will say they sound better than expected.