The new head units ARE hard to get out.
I had issues with my first '07 an LE which had to be taken back and I upgraded to XLE. To read about that fiasco do a search under my user ID.
As for taking the head unit out, you have to remove the shifter knob and then the shifter cover, yes the one between the armrest and the console below the radio and then you can finally start getting at the radio. I watched my dealers service department take mine apart just because I am more into the technical side of things rather than being like the majority of the population hiding in the TV lounge!
As for options and staying stock... Their are none in the Toyota sense. The XLE headunit will not plug and play as it has the 400 watt amp in the system and wiring harness' are totally different. And no one is making a kit to convert that yet to my knowledge.