Just bought '08 with 189k - drives like a dream, anything I should do now?

Buy a cat security shield. You'll thank me later.

Cat Security™ 2004 - 2009 Prius

 

These things are oil burner after 150k. I would do a oil burning check to get an idea how bad the oil burning per 1000 miles.

The dip stick has two dimples and the top dimples indicate full oil at 4 quarts. The bottom dimple means your down about 1.5 quarts.
Never let it drop below the bottom dimple!!!!!
All ways keep it full of oil.
How to check oil burning:
1st make sure oil is full at top dimple. The car needs be on level ground.
2nd drive the Prius normally for 1000 miles and see if the oil drops.
3rd if the oil drops on the dip stick. Fill oil back until top dimple. The measurement of oil lost per 1000 mile is how it take to get back to the top.
Special note. Prius can burn up to or more at 1 quart for every 1000 miles. If you find the oil burning is lower then address the oil refill according.
Enjoy your Prius.

SM-J737T1 ?

 

did i miss the plugs and fluids?

 

I would Drain and fill the ATF WS in the transaxle every 100k miles.

USA is pretty vague, if it is at all humid where you live I would have the dealer bleed the brakes. They are unique, and tricky.

 

I changed the transmission fluid (along with engine oil and filters of course) when I bought my prius (at 218k km) and didn't regret it - there was metal on the plug and some could be caught using a magnet, so I guessed it was probably never changed.

 

I bought a 2004 with a failed HV battery and 165,000 miles. The car was free, basically, but I did have to sink a bit of time to fix the battery - it can be done, if you're interested to do it and willing to learn carefully how. I did have to spent a lot on new front/rear/emergency brakes because the car had sat for more than a year and there were some old car issues like (expensive) rear struts and gas tank supporting straps and a new water pump.

These cars can go to 300,000 miles, and hopefully your 1-owner is a good candidate for that. I would suggest you bring it to a mechanic you trust at least annually and ask them to look it over, because older cars are more likely to have things go wrong, even though the Prius cars are very well engineered and built.

If you'd like to know the answer to that question that causes many used/old Prius owners fear... and you own an Android phone or tablet, I'd suggest you download the Dr Prius app and pay the $8 for the paid version that lets you test the HV battery, if you're interested in trying that. Likewise, the Toyota dealer may be able to do some sort of HV battery test. The Dr Prius app has a battery life test and another 'while you drive' test. The battery life test involves you sitting in your car with the A/C on/off, turning on/off headlights drawing a lot of power for about 10 minutes, after which it gives your battery a percentage grade. 40% is 'not great' but anything 60%+ indicates you're doing fine.

And, if the HV battery needs repair/replacement, there are independent providers who can do this for you for the price of rear struts, basically, so it's not such a fearful thing anymore...

 

If you use good quality oil with a decent detergent package and changed every 5,000 to 10,000 mi there should not be any oil burning problems. However, it is a good idea to do the check and continue checking until you are confident how much disappears.

I will add my take on this:

The dipstick has two dimples and the top dimples indicate full oil at 3.9 quarts. The bottom dimple means you're down about 1.6 quarts.
Never let it drop below the bottom dimple! Always keep it just short of full of oil, that is, fill with 3.7 qts. This should be 1/4" to 3/16" below the top dimple.

How to check oil burning:

1. Make sure the oil is 1/4" to 3/16" below the top dimple. The car needs to be on level ground.
2. Drive the Prius normally for 1000 miles and see if the oil drops.
3. If the oil drops on the dipstick, fill the oil back until it is 1/4" - 3/16" below the top dimple. The measurement of oil lost per 1000 miles is how much it takes to get back to that 1/4" - 3/16" below the top dimple.

Personally, I would not worry too much about filling back up until it was approaching the bottom mark. Of course, you will need to be very vigilant if you pursue this strategy until you become very confident of the quantity of the oil that disappears per 1000 miles.

The reason I recomend this approach is my oservation that if you fill to the top mark 1/4" to 3/16" disappears very quickly. If you fill it again it just disapears. If you leave it stays at around that level for quite awhile. If you do find oil disappears, it will be a lot less using thos strategy.

YMMV.