The reason being is that the third generation Rav's run led tail lights which cannot take the kind of current drawn by conventional trailer lights, hence a harness with a "trailer control module" is required to intercept a harness at the front of the cabin In regards to the factory toyota hitch - it's definitely a 2 man job and about half a days worth of work there are reinforcement brackets that get bolted in a multi-tude of places allowing the car to tow 1900kg worth (the box is ridiculously heavy - make sure you have someone to help you get this in and out of the car if you decide to purchase it, i can't remember how i managed to get it out by myself) The instructions should be easy enough to follow, the hard part is cutting your bumper to allow the hitch receptacle to protrude - I did this with a dremel which made this much easier - (it's just something that feels weird to do) If you do decide to DIY make sure you have all the required tools, including a torque wrench Price wise it was actually pretty decent - i think all up it was roughly around 600 inc harness and ball about a yr ago