Maintenance Required is just triggered by mileage since the last time it was reset. It's like an alarm clock for checkups. There's not necessarily anything wrong with your car, but a trip to a non-dealer mechanic might not be a bad thing. (Or you can go to a dealer if you want them to make/break something up just to charge you for).

Check Engine is the other light that means the computer decided something's broken and actually needs fixed.
No, actually, I wouldn't.
The dealer is in the business of selling you new cars. Put your car in their hands and you might end up needing a new one.
A real mechanic is in the business of actually fixing your car and keeping your business that way.