I can't speak for the 03, but Here are some pictures of the 140 dollar hitch I put on my 2000 Tundra..
Here is the hitch before installed:
Here is the underside of the car Before the hitch:
Here is the underside of the car After:
Only three bolts per side, and one alignment hole that goes over a nub on the frame.
Here is the Factory location of the wiring harness hookup. You get the brakes, running lights and turn-signals here. The Aux Battery Hookup, Electric Brake drive hookups have to come from other wires..
Another shot of the bolts:
Notice that the bumper is in no way attached to the hitch.
This was very easy to install myself by the way.. All you need is a torque wrench and a socket set.