I own a 96 LS400. I picked it up with 75K with all records, a one owner. It's got a 112K on it now. Runs like a dream. I didn't do the 90K service till about 102K but, never had a problem. I spend $1600 to get the 90K (timing belt, water pump, tune up, breaks and by my choice, the shocks, to keep the great ride). I didn't do it though the Lexus dealer but, a small shop of some guy who knows his stuff and I made sure that he would only use Lexus parts (I double checked the part numbers after it was done).
I hope to have the car for 4-5 more years (I hope less) till, I could afford a LS430. The only thing I wish is I got a 98 with a nav system in it.
I've owned Fords, Chevys, Hondas....The LS400 is the best car I have EVER driven and owned, and worth every dime. I don't want to ever own a different car.
If you can get the records and make sure the service was all done, and taken care of correctly, I would not worry about it that bad, as long as you can get a good deal. It's a car that will last and from what I read, that it's one of the best built cars out there.
Wise man never pays blue book for a car....shop around, you'll find the car at the right price...