Thanks very much for the reply.  I suspected it would be something beyond my level.  My son will be disappointed but I probably won't replace it right away since I'm not sure he is ready for it right now anyway.

Hi, I should start off by saying I am a complete model train newbie.  My 5 year old son yesterday received a Bachmann Santa Fe flyer. The train had never been used before but seems it must be about 15 years old by the packaging (It has 2003 markings  and the directions).  The backstory is that it was originally given to another boy many years ago who never played with it and since outgrew it.   It is an HO scale, and labeled as an EMD FT Diesel.  The engine appears to be the F9 on the Bachmann website. My son was very excited to receive it and has been playing with it pretty much non-stop since we got it. 

The train worked well for about a day but has suddenly stopped.  It seems to be connecting to the rail properly and with the cover off, I can see the motor is turning, but the white plastic gears do not. I apologize that I am fairly clueless on how to go about fixing this. I do not even see how I would take off the trucks to examine the gears or how they connect to the motor.  Any advice or suggestions are appreciated.