anything is possible if you have the money.
leather seats can be had if you go 3rd party, but your looking at 1500-3000.
kdss equivalent can be put on, but again its going to be 3rd party.
3rd row, I have seen someone put in a 3rd party rear facing bench, there is a post somewhere here but it was strictly kids only as you could only access thru the rear door.
and the pre-made version is the lexus gx460, but a brand new one will run in the 55-60k range or a used 1yr will run about 50-55, 2-3yr will run in the 45-50. that's assuming your going cpo, if you remove the cpo you could drop the price another 1-2k.