In 2019 I inherited a 1998 Chrysler Cirrus LXi (6 cyl) with 42,000 miles. My mother was original owner. Runs great, and I have put 25,000 miles on it in the past year!

Last week it didn't seem to be running right with bad fuel mileage. A few days later, check engine light comes on and it's "misfire cylinder #3". Next day, as I drive it in for the diagnosis it seemed to be running well and back to normal. The engine diagnosis finished and they find nothing. They reset Check engine light and it's still off for the last 2 days and running fine. I will check fuel mileage on next gas fill.

2 Questions. #1 Should I get a 2nd opinion? #2 Maintenance recommendations are tough because everything is 22 years old! Except normal oil changes. What should I be concerned with because of age? Transmission fluid, coolant, belts, etc? Should I just start replacing items because of their age? What should I start with?

Thank you for taking time to read this and any other suggestions appreciated.