Hi Alan - I am new to the club but not to LS400s - my first (1993)one ran to 350,000 miles and is now retired, not because it has any major faults but because I found a superb low mileage, historied '93 for sale. I have had some nice cars, but nothing comes close to the LS for reliability, comfort, (relative) economy and inbuilt quality.
So buy it, do not skimp on servicing, and you will not ever want to change.