Thanks for your help.

Would I need to remove the black and red wires that go from the left and right rails to the light board and instead solder to the 750 or leave them soldered to the light board? 

Thanks.  Would soldering the wires be the only thing I would need to do?  Do I need to isolate the motor terminals or is this already done since it is DCC equipped?

I just received a DCC equipped 2-8-0 N scale loco and tender.  I am trying to install a TSU-750 sound decoder.  From the instructions there is a note about the DCC board can be cut from the main board.  I see small holes where the two boards can be cut apart.  Is installing the 750 as simple as cutting off the DCC board, soldering the wires from the 750 to the holes in the main board?  I am guessing that the connector from the loco would remain plugged into the main board.  But I don't know if I need to keep just the one board or get rid of both boards and try to solder the wires from the 750 directly to the connector from the loco.  Also, I see instructions that say to isolate the motor terminals (from the 750 instructions).  Do I need to do this?  Seems like since it is already DCC equipped I don't need to do this.  Any assistance would be appreciated.  Thank you.