No, they don't have a chain, they have a belt and if it snaps it will cause expensive engine damage (it is an "interference" engine on the IS200). The original schedule for cam belt change was 100,000 miles, but Lexus revised that down to 60,000 miles (or 6 years). It's easy to take the cam cover off slightly to have a look at the belt, to see what sort of state it's in.
There's a guide on how to change the cam belt over in the Workshop section, with pictures.