I have an '07 Prius, it now has 124k on it and has been nearly zero repairs, doesn't use oil, no leaks of any kind, still on the original hybrid battery.
Regarding the headlights, I had the familiar problem of the intermittent HID bulbs. This is a $300 per side repair at a dealer, I bought a Philips bulbs off Ebay for $45, and took me about 20 mins to install. Check out youtube videos, you DO NOT have to disassemble the front bumper etc. All you have to do is loosen the radiator guard and a couple small brackets and/or fuse cover and you can access the bulbs. Granted, it's cramped and you have to do it blind, but if you familiarize yourself with what you're feeling for before you dive in it's not that bad.
With mine the passenger side went intermittent at about 110k, I replaced the bulb and it's been perfect ever since. About a month after that the driver side went intermittent and I replaced it, but it's still intermittent. Maybe I got a bad bulb, I've read online that a number of people have had that happen. I bought another bulbs but haven't bothered to install it yet. I figure it's either the bulb or worst case the ballast, which I'm really hoping to avoid.
Anyway, look on youtube, the HID replacement is not that tough.
FWIW my Prius seems to like most any 5w30 oil I put in it, but it LOVES Mobil 1 AFE 5w30. Just sounds so smooth and I swear it gets like 3-4 mpg more than the other syn oils I've used in it. I do 10k OCI's.