The LS400 is a fantastic car you will LOVE it. My father has a 98 (same as 99 or 00) and its what originally drew me to Lexus. I had a very hard time deciding between the LS400 99 or 00 CPO or the 03 ES. I finally got the ES because I had to lease for tax reasons, and the lease on the used LS didnt work out. Its a fantastic car, one of if not the best on the road. My dad's has 140,000 miles and its like brand new. They run forever, especially if you treat them well.
The CPO is great, the warranty is almost as good (if you get low mileage, it can be better) as the new car warranty. Its three years from your purchase of the car, or 100,000 total vehicle miles. They do a very comprehensive inspection, repaint any damage, do a full detail and replace the tires. Its the closest you can get to new. You do pay a price premium for it, but I'd go for it.
You're in luck because all 99s and 00s have the moonroof, the VSC, 6 disc changer and the HID lights, Lexus didnt make them any other way. The navigation system is nice, but its not as sophisticated as the new Lexus system, very costly to upgrade the maps because its a hard drive that must be replaced at a cost of almost $500 when the maps get outdated, and its rare driving up the price.
I live in the DC area, and I've seen probably all those blue LSs (I pop into the Lexus dealers often to see whats new and in) I'm going to PM you about one car in particular that I think you'll love.