100,000 service

Depends if you have a 4 cyl or 6 cyl....the 6 needs a timing belt and water pump, 4 does not. They will both need a 100k tune-up. If you have an automatic you should flush the trans. I'm not sure of when the radiator fluid needs to be changed?

As far as the mileage only maintenance?

Coolant system service.
Spark plug replacement.
Check your drive (accessory/serpentine) belt.
---V6 Motor (if applicable), Replace Timing (internal) belt.

It really all depends on what your maintenance history looks like.

It's a four banger with auto and fast approaching 100k. What should be done to maintain reliability and keep it in tip top shape.

change spark plugs, change power steering fluid brake fluid change engine coolant and transmission fluid. thats pretty much it honestly

clean Mass air flow sensor and throttle body too

Spark plugs for sure. I guess it depends on how you've taken care of your car and the service it has seen along the way. If its been over 3 years, do a brake flush. Coolant if you haven't done it. Maybe a new cabin and engine filter, and just for good measure, check your belts and hoses for cracks and wear. Transmission/diff flushes if you havent done one in maybe 30-50k miles depending on the kind of driving you do.