Hi 77, I hate it when I have to be there one to give bad news but Soundtraxx decoders do not work in analog mode. :( . I copied this from there help topics, Locomotive never ran. Locomotive is not on a DCC powered track. SoundTraxx Digital Sound Decoders do not work in 'analog' mode.
A Digitrax DH163AO, DH163D, or a basic DH123D should be the decoder you need anyone of these will work. As far as getting the shell off I am not sure, take a real close look at the parts diagram that came with the loco.
Hey Mike
When you say Bachmann start up set I take it as Bachmann Easy DCC, the Lk100 should work ok. If you need it here Lenz web site the manual for the LK 100 is there.
http://www.lenz.com/manuals/index.htm
Hope this helps. also MRC makes a reverse loop module.
I'm not positive on that loco but you'll probably have to hard wire it. Mfg's alot will advertise DCC ready when the loco has a split frame and the motor is isolated. You might try contacting Tony's Train Exchange they should be albe to set you up with the right decoder...