I just put in an AVIN for my son in his 2006 4.8is. with factory nav and DSP. It was NOT an easy job. The quotes I had from install shops was north of $1k. Thus I did it myself. You literally take apart most of the interior to install if you have those two options.

The video showing how to do it is good up to the point that they show the connections, and somehow with 4 wiring harnesses that is supposed to be intuitive.

It works great now that it is all together, would I do it again probably now that I know how but it wasn't a simple job.