NPComplete,
While snooping around an indie shop earlier this summer, I overheard a mechanic mention he was doing a LS400 90K service after lunch. Bear in mind, this was a Friday afternoon..........so the car would be ready by five o'clock.
Now, usually the 90K service is the t-belt plus all fluids, filters, etc.......
This guy was going to knock it all out in 4 hours (lunch was noon to 1pm).
Now, I don't know for sure this was a full blown t-belt service.........but I got that impression.
Those Idler pulleys & the water pump take a little time (but not much for a pro)---but the timing belt tensioner is total cake (and the dealer knows it).
With all this being said........you could probably save another $200 at a reliable independent shop; But maybe you can find a coupon (10%) online or something to make up the difference. Call around and follow silvermates advice :D
Expensive, YES! But over 5 years or so its not so bad. Plus No Stress for you!
You'll also need some serious tools.....most DIY guys take 8-12 hours; so it will take up your weekend for sure.