Rivarossi Y6b question

[nw-modeling-list at nwhs.org]

I need a little help here. I have three of these. I am planning on putting 
DCC decoders in them. I have one of them open on my workbench now. I need 
help in determining:

A) which wires are for what - from my eyes it LOOKS like the motor gets half 
its power from a pickup on the engineer side wired to a contact on the motor 
and the other side of the power through the locomotive frame to the case of 
the motor. I have figured out how to isolate that to get to the DCC decoded 
I think.

B) how does the headlight get its power? I can see one wire that leads from 
the motor case to the front. Therefore I am assuming the other half the 
bulb's power is also coming from the frame? I am scared to tear the thing 
apart much more without knowing what I am doing. I had a lot less trouble 
putting a decoder in an early 60's Mantua Pacific in the course of making 
N&W #578.

Any help would be appreciated.. feel free to post it here or email me 
directly at bob at firedogwireless.com. If putting my email address in this 
post is taboo, Mr Moderator, please edit it out and send the post on... I 
really want to run something other than a J, the E2 or an inappropriate 
2-10-0 on my newly-updated to DCC layout....

Bob Welsh