Scott and crew just bought theirs a few months ago with 225k, so no, it isn't too high to start. I would look really hard at the maintenance history. (available from any lexus dealer, so the selling party should be able to provide it) As long as it has been well maintained, the engine should get you to 350k before "needing" a rebuild. If it is a good price and well maintained, I would pull the trigger, but if other rigs are selling for the same price with less miles, wait.
The Lexus has the plastic body cladding which some folks like, others don't--it protects the sheetmetal a little, but I could go either way. "The lexus has a subwoofer" in the center console instead of the cubby that the LC has. Supposedly it is easy to remove, but either way, that space is better used as a cubby/cupholder. The lexus also has a 6 disc cd changer in the back of the center console instead of an in dash cd player--may or may not be an issue depending on previous audio mods and your plans--many folks have put power inverters in that space.
The LX should have a little higher grade leather, but being from NM, I wouldn't expect it to be in great shape.
If the lexus came with the car phone, one of your third row windows will be fixed instead of sliding--this is an issue with dogs and can be fixed by getting an LC window to replace it. The LX also had a little bit softer suspension, but I imagine that you will be replacing that anyway.
I am sure I am forgetting a couple things, but for an exhaustive list, there are a couple threads on mud that detail the differences.