Your brakes shouldn't "clunk", that's not right. I'll leave others to comment further on that.
As for the parts, try CheapToyotaParts, I got my water pump from them. Also don't forget to try Lexus/Toyota for a quote too, and if you're a Gold member you can get a discount from most dealers.
Did you not get instructions in your HID kit ? All you really need to do is unplug your headlamp bulb, connect the existing car's headlamp plug into the HID kit, and insert the HID bulb into the headlamp, then fix down the ballast somewhere convenient (e.g. with strong sticky pads).