When was the last hybrid battery replacement? Reconditioned ones on the web are about $2500 -$3500 installed. I don't have one but I recall reading around 100k. As far as the rest of the car, It has a CVT so look for the service records on fluid changes. Is this Rear Wheel or AWD? If all wheel look to see if the front transaxles have been replace. The way it was explained to me a boot tear itself can be fixed but the labor for one side is so high the mechanics just want to replace the entire unit. Mine went at about 120,000.
Outside of that these cars had some dash rattles due to screws in the dash loosening, the easiest fix is to locate and push some felt in the gaps to tighten it up. I only had one between the instrument cluster and the dash on top.
I never viewed the MPG on these cars as much or any advantage since it is only slightly better than the 350 and slightly quicker. However if you drive mostly city then the fuel savings at todays prices and the low price of the car makes sense.
On the website Fuely people are saying they average 25MPG combined. I get about 18 around town and 27 on the freeway.
So lets call it 21MPG combined. If you need a new battery at the $2500 and if your gas is $5 per gallon, according to an online calculator I used ( should have learned my word problems) you will be saving $496 per year driving 12,500 miles. If you live in Cali with premium at $6 then the number changes to $571 per year. So the battery pays for itself in 3-5 years depending on gas prices. But then you have to factor in the age of the car and how many more miles you can put on it. I would think you can easily go to 250K -300K given your description. So if you keep it a new battery makes sense
Also if he/she serviced it at the dealer I have had good luck giving them the vin number and having the service manager pull up the records.