Feel free to ask questions. We're a friendly group who likes talking about our cars - which we love so much.
I personally would go for a late LS400 simply because an early 430 will be almost as old and potentially more of a money pit because there are more gizmos to go wrong.
I'm so glad I bought mine when I did because there weren't many around then (four years ago) and there are even fewer now. You're right - I think prices are rising, and mine's probably still worth what I paid for it. Which, when you add reasonable fuel consumption (on a long run) and mechanical toughness, makes for quite cheap motoring especially if it's not your main car.
Because there aren't many left, you may have to be less choosy than I was. Whatever you buy (at a sensible price) will need work of some kind, but I suppose the issue is what kind of work. It's been said many times before, but maintenance/history is more important than low mileage. Mine has done 150,000 but I can't believe that a 50,0000-miler would run any more smoothly.