I recently had the passenger side headlight burn out on my 2008 Prius. I got a bulb from NAPA for less than $9, then went to the internet to see how to install it and wasted hours with some "really bad" instructions!
Long story made short, I was able to remove a black plastic shield near the windshield washer tank, then get my hand behind the headlamp and unplug the connection and rotate a soft rubber cover counter clock-wise exposing a wire bail which holds the bulb in place, I then removed and replaced the bulb.
The whole process took about 15 minutes, I hope this helps.