I installed a LokSound Micro in the tender of mine and utilized all the power pickups of the loco and tender.
I used Ngineering's flex wire running between the loco and tender and used some tiny plugs to allow the tender to be separated from the loco.
Needless to say, I got a pretty good understanding of the loco. Luckily for you, I took pics along the way and already have some of them hosted. (usefull since I'm at Road America in WI for the AMA Superbike races instead of home in Portland, OR)
The driver sets each have a small black wire that comes up the side of the frame and run to the motor. I've got more detailed pics at home and I can post them up when I return home later this week if you'd like.
Here's pics:
(Sorry only big ones hosted)