If possible, see if you can find a hybrid garage that can put in a battery from the Gen 2 Prius. It's a bit more powerful and possibly cheaper as they are more Gen 2s and there should be more used batteries around in good condition.
- Note that the Gen 1 uses XL (extra load) tires so keep that in mind when replacing those.
- Check the 12V battery and see if it's been replaced recently
Note that if the battery is low, the 1st Gen Prius will go into "Turtle Mode" and you'll see a little illuminated turtle on the dash. Typically won't happen unless you plan on crossing the Rockies or Appalachians regularly with a full trunk. Newer Prii are capable of maintaining speed without the battery's help on the highway.
Here are a few things I found from a Gen 1 owner:
The more salty your winters are, the more you need to exercise the parking brake cable and inspect the condition of all brake hardware wrt corrosion. This is a downside to friction brakes with a very low duty cycle! Absent that, anticipate 200k brake life or more. But, as with all hydraulics, the fluid will absorb water over time and one should enlist the help of a competent brake shop to confirm that you are not above 1% water. Fluid replacement otherwise.
For (nearly) all NHW11 used buyers, find out if the HV battery resealing and crankshaft position sensor have been done. Free by Toyota with no sunset. The most common squawks are ECM and power steering replacement, both of which should have been done (by now) under warranty for affected vehicles. Some bad accelerator pedals before VIN ... 45000.
This thread could help: