It depends what is wrong. Your car has an idle air control motor that should automatically adjust the idle speed. If the car stalls particularly first start from cold in the morning the idle air control valve on the bottom side of the throttle housing may be defective of just need to be cleaned. Call an independent Toyota or Lexus repair shop in your area they will have seen the problem before ask them do they clean or replace the IAC, I clean them and never have a problem.
A low or high idle speed may be caused by something else but some diagnostic checks would need to be done to isolate the problem.