Damn. Since it's probably too late to talk you out of it...I'll throw in some suggestions -- most of which I'll just be echoing what others have already stated...
Do yourself a favor and replace the chrome wheels with something else when you take that puppy offroad. Or, save the chrome ones for city/highway only. It’s kind of a shame to thrash them. I beat the crud out of mine and now wish I’d picked up aftermarket wheels from the start.
The “chromed” caps are crap. They’re not OEM Toyota. They don’t stay on well. I lost one…then lucked out and found it on the highway median strip…then lost it again a week later. Toss them…or buy my 3 caps
The center console – don’t trim anything. Check all the screws on both hinges. I’d bet that some of them are loose. I found that if they’re loose, the top doesn’t sit properly.
The pitch and sway is common to LX 450s. The rear springs on the LX are the same springs that are used on the non-third-row-seat LCs. I’d guess the spring rate is a little different. That plus softer shocks will give you that floaty ride. Go OME and you’ll be done with that.
I would just drain and refill. If it looks funky when you drain…then think about flushing. Based on what I’ve read though…I’m pretty wary of tranny flushes.