I replaced my timing belt on my wife's RX330 and it was not that difficult. Just make sure that you have a crank pulley holder tool (available from SPX OTC) and the repair manual. The only difficult/tedious part was removing the a/c and p/s belts.

The job is well within the capability of any decent mechanic. Remember that this motor is shared with many Toyotas (Highlander, Camry, Sienna, RAV4 V6, etc) so it doesn't have to be done by a Lexus-only repair shop.

Some things to consider replacing (depending on age and mileage) during the timing belt replacement include the water pump, idler/tensioner pulleys, and tensioner. These are items that can be inspected during the timing belt change. I've changed timing belts on four Toyota/Lexus cars and saw leakage on one that had 10 yrs/110k miles.

 

Thanks to Sewell, I was able to get my necessary parts for the timing belt job for $396 shipped and with my brothers buddy doing it for $300 I will have everything done under $700. I was really suprised at the discount Sewell gives us CL members, thanks you Sewell! Saved over $100 list price!

 

I just had my 2004 RX330 timing belt replaced @ 124,000 miles. I asked for my old one just to inspect, & well cuz its mine. The old one looked very clean, probably could have gone for awhile. But if timing belt breaks, car wont run (properly). Wasnt that bad, bout $400. Water pump is $350, but didnt need it replaced (they checked).
Also @ the time they did my floor clip recall. And yes, they did refill my tank. I drove half the tank so i figure about $32 in free gas. No major problems with car. Oh, i also replaced some worn belts. $70 i believe.
Good car. put 300 miles on it every week since sept 2010 driving from one city to the other.