Replacing coolant parts as a safe measure

Get your heat exchanger bypassed, change water pump, plugs, pcv valve, CVT flush and just drive it. We have the most economical and reliable version of the Prius ever..don't over think it and worry.

 

when you say it has been neglected, are you the first owner and have neglected it, or was it a previous owner?
if you purchased it used, how many years have you owned it, and how many miles?
do you know the full maintenance history, and do you have the maintenance schedule that came with the car?

 

Welcome and sorry to hear that.
My sister lives in northwestern Mississippi and gas prices are so cheap - return on investment is questionable at best for paying the extra money for a hybrid - relatively speaking.
There's a litmus and glycol test, that can be done to check the condition of your coolant. Changing them both at the same time, just makes it easier to keep track of what's been done.
IMHO; Shocks and rear brakes needs inspection - Unless they can prove that there's a problem, they don't need to get done. That's a want, not a need.
You should install one of these P10 HUD unit:

It plugs into your OBD2 port and monitors your engine temperature. Alarm limits are programmable and will beep at you. Your onboard warning lamp is set for 248F+ before it lights up, I'm pretty sure without an alarm. Normal operating range is 185F-210F, so early warning system when your electric water pump is beginning to fail. If you don't notice that coolant lamp flashing at you, you could pop the head gasket or worse.
The transmission ATF should probably be changed, It's probably black as tar with 171K on it. Simple drain & fill around $150-$200. That fluid should be ruby red.
Spark plug replacement is overdue; if that's never been done. I believe that interval is around 120K miles per OEM.
The 2016-2018 had issues with the exhaust gas heat exchanger leaking, so you should check the coolant levels in BOTH coolant tanks every once in a while - make sure it isn't getting low. Someone above mentioned by-passing it, to keep repair cost down. Doesn't need to be done unless you keep losing coolant out of the passenger side coolant tank.

Good Luck...

FWIW: I actually talked my sister out of buying one, because of the lack of qualified mechanics along with the cheap gas prices over there. The economics coupled with neither of them being able to 'wrench', left them vulnerable to dishonest mechanics. At least with a regular car; you can take it down the street, to a more honorable mechanic.