06 lexus es 330 navi + parking sensor?

I have a 2006 ES 330 with a stock CD changer I'm looking to add Nav + Parking senors any idea the best route to go about this?? I'm sure I can go to the dealer ship but I have a feeling they are going to charge an arm and a leg. If I order the parts OEM is this something that I could find some one to install for a desent price? Would I save alot or should I just pay the dealership to do it? Any help would be appreciated.