What Is Needed To Add Navi 06gs300

[-the.k.w.c-]

I have a 06 lexus gs300 and it does not have navi.

I would like to know what parts are needed to add navi to the car ie ( gps computer, antenna, wireing, cd, whole new screen unit)

I know that a lot of car companies have all wiring already in the car so all they have to do is plug in a couple things. So if you guys could supply me a list of all objects i will need in order to add Navi to my gs300 that would be great. Im trying to piece parts together from ebay and wreaked cars.

Thx -Kevin