I have an older version of that TV (KP46WT510), which I presume to be very similar but a year older. When I first got it, I took it apart and lined the interior with Duvetyne and replaced the plastic screen with a non-glare glass screen. Unfortunately, that was five years ago, so I don't remember the details, but I do remember the bottom being hard to get off. I hate to tell you this and be wrong, but I'm pretty sure brute force was the fix. I THINK it had those springy clips similar to what you might find holding on some panels in cars. I think there were several of them, and you have to work your way towards where you can tell one is, then try to pry as gently but firmly as possible while trying to contain the force to the area right around the clip.
But once you do get the front panel off, the other three screens are taped together as one, then attached to the front bezel (can't remember if it's screws or clips). You just need to undo the tape around at least three sides, then open up the sandwich. Yes, the "contrast" screen is the outer screen. FWIW, in case you're interested, I replaced it with a non-glare glass that you can find at framing shops. It's a smooth surface, but it has some kind of (metallic?) coating on it that reduces reflections. It gives the glass a green cast to it, but it's really the reflections that are green, not the light that gets passed THROUGH the glass. It made a big improvement in glare, and it was also nice having a hard flat screen instead of a flimsy wavy plastic one.