I had to replace the bulb for one of the Day Time Running lights on my '13 Energi. To get to the bulb you have to remove the headlight assemble from the car. To do this, you have to remove the front bump cover, which is a fairly involved process. There are several different types of fasteners, including standard 'rivet' fasteners, screw rivet fasteners, two different size hex head bolts and two difference size Torx bolts. Since I was only replacing one side, I didn't fully remove the bumper cover, just pulled it away from the front but left the other side loosely attached.
Once you get the assembly off, there is a single wiring harness that pig-tails off and connects to the headlight and the DTR light. The headlight is secured with a wire clip, that is pretty straight forward to remove. The DTR light bulb is a little more difficult to get out. To remove it I used needle nose pliers to squeeze the socket and was able to pull it up and out. I could not find a spec for what replacement bulb to use, but the old bulb was a 5 watt, so I found replacement Sylvania bulb was close to 5w (4.7w) and it fit. I used Sylvania 161 bulbs.
Definitely not a 'fun' job, but I'm sure the dealership would charge a lot to do it. Overall it was a very involved process but not too bad. When the other side goes I'll do it again.