Check Engine light turned on, it okay to drive my car?

Hello,

The check engine light gets triggered when the onboard diagnostics detect any fault within any of the vehicle operation systems. It could be anywhere from an emission error to faulty sensors. It could even be as simple as a bad or loose fuel cap.

The best course of action would be to scan the vehicle and get the code(s). This can determine what might be the reason.
Without knowing the code, it is difficult to say if it will be safe to drive.
Most auto parts stores will have diagnostic scanners that can be used to retrieve the codes.

Here is a helpful guide:

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

Let me know what the code(s) you get or if you have any questions.
Thank you.

I think my air filter needs replacement! (29,000 miles).

If the air filter hasn't been replaced since the vehicle was new, then yes it will need to be replaced.
However, a dirty air filter will not trigger the check engine light.

Dealer is asking $140.00 to check codes, my mechanic will charge me $20.00, no brainer.

You can also go to your local auto parts stores (like AutoZone, Oreilly's, Napa etc.,) to have the code read. They will do that for you free of charge.