It seems doable enough, according to YouTube Videos, that one can change their HID head lamps, without removing bumpers or body panels. So I went on an exploratory mission to do just that. After noticing that the left hand head lamp will switch off & on, intermittent times, it was time to make a change. The wife purchased two bulbs, so might as well do both, right? The very 1st obstacle is that I am having a bear of a time, removing the cover. I 1st took the fuse box cover off, that also houses the battery terminal for those jump starts you may need. Then I attempted to remove that cover to no success. I read that a hair dryer could aid in their removal. I am also beating the bushes here, to see what may have been the best manner of accomplishing the task of replacing HID head lamps.
There's a bunch of videos on YouTube on how to do this. Look on YouTube for headlight replacement or removal for Prius. Good luck.
A lot of us have found the plastic cover on the driver side too tight to turn by reaching one hand in there without removing anything else, as the woman from Luscious Garage does on YouTube. I didn't think to try loosening the fuse box as some including yourself have tried. I ended up starting to remove the bumper cover, but I also struggled to remove some of the bolts securing it. Luckily, once the bumper cover was loose enough on the driver side I was able to pry the entire headlight assembly out of its socket. After that removing the plastic cover behind the headlight was no problem. I had much less trouble with the passenger side headlight, which I changed at the same time. This link describes some of my issues and solutions, as well as those of others. Does '08 Prius require HID headlights? Dealer wanted $160 part/$21 install | PriusChat I hope this helps.