I started a thread about parking sensors a little time ago, and found out exactly which models had them when. It's here, if you want to look, or the most relevant bit I wrote was this:
"As best as I can now tell, the sensors were not available at all at launch, became available as an option in March 2001, and became standard fit in April 2002."
Full thread at
http://www.lexusownersclub.co.uk/forum/ind...parking+sensors
As others have said, premium pack is basically the rear massage seats/aircon/radio controls, and fairly useless rear coolbox.
And welcome to the club!