I want to install a DCC decoder in the N scale 4-6-0 locomotive and tender that comes with the Broadway Limited RTR set.  I can see the conductors that are integral to the drawbar connecting the tender to the loco, and I can see the copper strips in the bottom of the tender, but it's not clear to me whether the loco needs to be opened and modified, or if additional conductors must be installed between the loco and tender to do this.  Can anyone summarize for me the modifications necessary to do this?