They go right in. My '05 has the RB1 which I think is a better unit than the RB4. (I could be wrong on this, check them both out & decide)
The install is simply plug & play, not issues at all.
The antenna can be placed anywhere inside the dash, mine is stuck to the top of the radio. As the body is composite it doesn't affect the signal like a steel bodied car does.
You don't need a wiring harness, it uses the same connector as the original radio, & works perfectly.
By the way, Chrysler also makes an Ipod adapter that works well with this combination. Installation is once again plug & play, but you will need to devise a location for the plug. Most of us have used the center console pocket for the Ipod placement, simply route the wires around the shifter, drill a hole in the plastic for the cable (this is inside the storage compartment so it doesn't show, and there is a grommet so it looks like it came that way from the factory), and it works like a charm. Even shows the selections, artists etc. on the RB1, and all the controls are through the RB1.
Regards,
Mike Dolan