I picked up a deck on boxing day, and installed it today. I read online with some confusion as to what harness to employ in this task, so I just picked one and ordered it on ebay. Turned out it was the right one.
METRA 70-8112 TURBOWIRE for Toyota/Lexus 92-99 amplifier integration
this one has 4 RCA Plugs and then the regular wires.
It doesn't appear to line up to the stock harness to allow for power antenna, so if you have one (I don't know if this is a feature on any of these cars) then you have been warned!
My X105 has the subwoofer in the rear deck, and I presume the amplifier ! HaHa!
Removing the stereo cover is pretty easy, first you need to remove the base around the shifter (mine is an auto). Pry gently near the armrest, and it should pop off the clips. Then pick a spot on the stereo surrround and gently pry, then work your way around. Once you are in, remove the two harnesses in the surround for the cigarette lighter, and the trim is gone.
remove 4 hex bolts (likely 8/10mm or so, I can't remember) and the whole assembly will come out. Then do your business!
One note, there seemed to be an extra antennae plug that was a tad smaller than what I'm used to seeing. I'm not sure what it is, so I tried my deck before reinstalling to confirm am/fm operation and it worked great, so I taped it up with electrical tape, and tucked it away.
As for audio, the overall sound is quite good in my Cresta, so I won't be changing or adding anything there. I'm pleased.
I'm curious to see what others will do here though, so post away!