I am trying to access the gears on this train that I just acquired, and I am guessing that I need to remove the truck cover plate to access the gears.  However, I am unable to see how this comes off.  An online video of a newer model indicated that you could use a screwdriver to simply pry it off, but when I tried it seemed I was pulling the whole truck unit through the train frame.

Any help or guidance or reference to online resources/videos would be greatly appreciated!

Train is a Santa Fe 307, EMD F9 diesel.  Part of a 1982 promo set.