Just picked up a 2001 IS300 with 123K. I know the lower ball joints will need to be replaced. What else in that are should I just change out while tending to the ball joints?

 

Suspension wise? jack the car up and look at the bushings for cracks or wear; lower control arm, upper control arm, tie rod ends, sway bar bushings, motormounts, check the shocks to see if they're leaking, inspect the brake lines for cracks.

At that mileage, make sure the timing belt service has been done, if not, do it asap. I'd also flush the fluids; power steering , brake, coolant and transmission fluids.

 

Sway bar endlinks and swaybar bushings are also suspects for creaking over time