Bought a used 2007, now I'm worried

Headlights are potentially do-it-yourself. Slightly trickier than on some other cars, but well within the realm of possibility, unless you have the HID headlights. Those are a real pain to get at and expensive to replace. Which type do you have?

As for the battery charging/discharging, that sounds normal.

 

Does the ICE (internal combustion engine) cycle off at stop lights and can you drive without the ICE in town up to 40 mph for about a mile? If so, the HV battery is probably ok.

 

You may want to check the small 12v battery. There is a test that is displayed in the NAV screen. If the 12v battery is weak it will allow the large traction battery to work harder thus depleating that battery charge. The cost to replace the 12v battery is under $200 plus 1 hour labor at the dealer.

12V batteries Last about 5 years. You may still have the original

How To Check Toyota Prius 12 Volt Battery 2004-2009 Models

 

I'm not a master mechanic . What you are saying is similar to the small 12v battery starting to weaken.

The dealer would be happy to test it for you if you dislike the self test.

Toyota Prius: How to Check the 12v Auxiliary Battery Health - PriusDIY.com

 

2G Prius (2004-2009) Standard and Optional Equipment (Some Countries) | PriusChat may help you identify which model you have.

I believe if you have foglights, you'll also have HIDs. (I have an 06 package NL so it has HIDs and everything except leather).

If you have HIDs, Philips D4R Xenon HID Headlight Bulb, Pack of 1 : Amazon.com : Automotive direct from Amazon (not a 3rd party reseller there) should be genuine and thus a safe replacement, as opposed to random bulbs on EBay, many of which are fakes.

 

Re: replacing HIDs, some people can do it real easily like Luscious Garage. See below.

My attempt turned into a disaster due to the spring clip coming off (can't remove washer fluid tank, trying to replace passenger side HID | PriusChat). I ended up having to pop off the front bumper cover. I'm nowhere even close to as adept as Carolyn at LG. I'd imagine that she and her staff have done many thousands of jobs on Priuses.

 

^^^
The directions to change the halogen headlights are in the owner's manual. The bulbs are much cheaper than HIDs.

I can't speak to the easy/difficulty vs. HIDs.

 

The Halogen lights are simple bulbs. Any "corner mechanic" can install them for you if you don't want to get your hands dirty. Should be no more than 30 minutes labor for both headlights.

 

There are a couple good videos over on YouTube re: Headlight replacement.
You can easily pay over $200 to have the dealer change even the simple headlamps.I had to pay the dealer the first time because I had a cop writing me up for a bad head light. I swear the cop saw it the exact second it blew out and gave me a warning. I was unable to budge the darn lamp myself. After the dealer loosened up the rubber boot, I was able to do future replacements myself thereafter, using the contortion artist method.