Definately go wiith a seperate circuit. Dont take the chance with the stock setup or you will be replacing the multi-function switch. It may seem like like more work to run the wires through the dash. But its really simple, mine run from the battery, to a switch, took less than an hour. If you want to keep an original look inside, mount the switch to the plastic under the steering column. Thats were mine is and you cant see it, except at night since the switch has a red light to show they are on.