yes, if the existing wiring isn't 100% good looking, it's best to replace with new - that's about the price they all have, and what I've paid - there will be 2 listed, one for "w/ generator", one "w/ alternator" ... the heater just uses an 'accessories' power source wire from the ign switch
also if the truck doesn't have a fuse panel, just above the pedals [they usually only added that if it was ordered with a number of acessories], it's worth
getting one, which usually include some accessory wires
Bill