Hi Ned,
The cheaper model in Lexus you are referring to is actually "TOYOTA CELSIOR" which is Japan domestic version of LS430. I own two of them 2002 & 2003 at fraction the price of designer's Lexus. there is no difference in anything except that all Japanese vehicle speeds are locked at 180 KM or about 112 Miles while their Cruise Control has a maximum speed limit of 108 KM. Sounds ridiculous but that's the downside with Japanese domestic models & you will have to live with it. I know some of the more enterprising owners have found a way to disable speed limits both on the dash as well as Cruise Control but, I am of a compromising nature hence happy with the existing arrangement.
As regards changing the language, again I have been told that the control unit installed in the boot contains language options on a chip, unlike some car versions that contain it on a DVD. So a proper chip writer is required to do the job. I have seen it done on an IS 250 successfully, but the mechanic was hesitant to try on my vehicle fearing that he had no experience of doing it on a Celsior.
I would suggest you to buy an Owners Manual in English as I have resorted to and every thing will fall in place automatically.
Best regards