It quite easy...Follow the instructions..I have put on two, one on my 03 RX1 and a couple of weeks ago on my 04...Tip, I got probably from this site..Clamp off the coolant hose above where your installing the heater..I used a couple of pieces of old slider and a clamp. That way you only loose about a cup of antifreeze and there is no need to bleed the system after your done..Careful when you install the heater..Install it so when you plug in the cord the cord runs upward not downward.. The instructions will show you where to route the cord..