i've heard truck drivers make really good money
It depends on what company they work for. Truck drivers provide essential service to industrialized societies 
so do you need a special driver's license to become a truck driver?
I believe so. I think you should have category A driver's license. Truck drivers also responsible for inspecting all their vehicles
so they also have to be mechanics??
no, they just needs to make sure the trucks are drivable, they inspect them for issues relating to safe operation like is the check engine light on, are the rites good, etc