2 questions...Does anyone know if my 2001 Lexus IS300 has a timeing belt or chain? Also What mileage do I need to think about getting it replaced?

Oh sheena almost got it right. The LS300 has the same engine as the Camry. The IS300 is a little different. Now the water pump is not driven by the timing belt but half the bolts are inside where the timing belts are so it would be a good idea to have it replaced when doing the timing belt. The recommended interval is 90k miles.

did you know that your lexus 300 is the exact same car as a toyota camry. buy the service manual on a camry and your car is listed. it has a timing belt and 50000 to 60000 is recommended. i will warn you though when you change the belt change the water pump as well. it will be your next problem after the belt is changed, because it runs off the belt as well. more tension =more pull on the pump bearings