The last paragraph here may help. [ http://www.spookshow.net/loco/mtsw1500.html ] I have the worst time getting into most newer N Scale locomotives.
I find that the least destructive way to disassemble these little guys is to pop the handrails off the cab..Gently wiggle the cab free of the body. Once the cab is free you can push the mechanism free of the body. The front contacts may twist a bit but they can be realigned with a pair of tweezers.
Thanks everyone for the suggestions. mtntrainman's suggestion worked beautifully. Now how do I separate the chassis? The two screws don't have slots for a screwdriver.
I remember having a locomotive frame with the same problem. From looking online at a picture of that frame...there are two plastic 'caps' that you have to remove to get to the screw heads. I used the tip of a hobby knife blade to pop them caps outta the frame. You dont need to put those %^&%$%$^& caps back in when done. JMHO
It appears to be a futile effort to let the contacts slide by the screw holes without getting ripped off.
When I do get a shell off that is held on by 'dimples', and it is as notoriously difficult to remove as many LL and Atlas, I take my moto tool with an abrasive disk in it and grind off about half the thickness of the dimple. Not all of it, about half. It will still lock down, but you don't have to nearly destroy the shell trying to get it off again.
Just for clarification. Its the 4 'nubs' on the frame you want to file down...not the 'dimples' on the inside of the shell the 'nub' sets into. 'nubs' stick out...'dimples' go in...