I have been plagued by the "side airbag" light coming and going off. Now the maintenance light is on permanently!

I have been diligent in having the oil change and have had two tuneups, keep the car in the garage and everything else that I think will help keep it in good shape.

I had a oil and lube job a couple of weeks ago (on time of course) and the mechanic could not find the problem for the maintanance light being on.

Is it time for me to go to the mechanic? Also, how do I know if the dealer is trying to make pay for something that I cannot afford and do not need?

If it is the Maint Reqd Light, press and hold the button that resets the trip odometer, turn the ignition on, don't start, and the light will either go out after about 10 seconds or flash for about the same time and go out. This is just a reminder light.
If it is the Check engine light, there will be a DTC and your mechanic should be able to find the problem. When in doubt, go to the dealer. The cost is usually higher but an independent garage is more likely to scam you.
A lot of time, Air Bag problems are a dealer only repair and should only be done by them as they have the proper equipment to diagnose such problems

Had a similar issue with an intermittent passenger side airbag light; turned out to be my wife's orthopedic seat cushion interfering with the seat sensor.